diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.cpp b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.cpp
index adb58c0d92..8a486a016a 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.cpp
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.cpp
@@ -51,6 +51,21 @@ void caf::AppEnum<RimSummaryCurveAppearanceCalculator::CurveAppearanceType>::set
 }
 } // namespace caf
 
+namespace internal
+{
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+RiuQwtPlotCurveDefines::LineStyleEnum cycledLineStyle( int index )
+{
+    if ( index < 0 ) return RiuQwtPlotCurveDefines::LineStyleEnum::STYLE_SOLID;
+
+    return caf::AppEnum<RiuQwtPlotCurveDefines::LineStyleEnum>::fromIndex(
+        1 + ( index % ( caf::AppEnum<RiuQwtPlotCurveDefines::LineStyleEnum>::size() - 1 ) ) );
+}
+
+} // namespace internal
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
@@ -514,7 +529,7 @@ void RimSummaryCurveAppearanceCalculator::setOneCurveAppearance( CurveAppearance
             m_currentCurveGradient = gradient( totalCount, appeaIdx );
             break;
         case LINE_STYLE:
-            curve->setLineStyle( cycledLineStyle( appeaIdx ) );
+            curve->setLineStyle( internal::cycledLineStyle( appeaIdx ) );
             break;
         case SYMBOL:
             curve->setSymbol( cycledSymbol( appeaIdx ) );
@@ -585,17 +600,6 @@ cvf::Color3f RimSummaryCurveAppearanceCalculator::cycledBrownColor( int colorInd
     return RiaColorTables::summaryCurveBrownPaletteColors().cycledColor3f( colorIndex );
 }
 
-//--------------------------------------------------------------------------------------------------
-///
-//--------------------------------------------------------------------------------------------------
-RiuQwtPlotCurveDefines::LineStyleEnum RimSummaryCurveAppearanceCalculator::cycledLineStyle( int index )
-{
-    if ( index < 0 ) return RiuQwtPlotCurveDefines::LineStyleEnum::STYLE_SOLID;
-
-    return caf::AppEnum<RiuQwtPlotCurveDefines::LineStyleEnum>::fromIndex(
-        1 + ( index % ( caf::AppEnum<RiuQwtPlotCurveDefines::LineStyleEnum>::size() - 1 ) ) );
-}
-
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.h b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.h
index 26ba4a6308..4b98a2f795 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.h
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryCurveAppearanceCalculator.h
@@ -18,7 +18,6 @@
 #pragma once
 
 #include "RiuPlotCurveSymbol.h"
-#include "RiuQwtPlotCurveDefines.h"
 
 #include "cvfColor3.h"
 
@@ -77,9 +76,8 @@ private:
     void updateApperanceIndices();
     std::map<std::string, size_t> mapNameToAppearanceIndex( CurveAppearanceType& appearance, const std::set<std::string>& names );
 
-    RiuQwtPlotCurveDefines::LineStyleEnum cycledLineStyle( int index );
-    int                                   cycledLineThickness( int index );
-    float                                 gradient( size_t totalCount, int index );
+    int   cycledLineThickness( int index );
+    float gradient( size_t totalCount, int index );
 
     cvf::Color3f gradeColor( const cvf::Color3f& color, float factor );
     void         assignColorByPhase( RimSummaryCurve* curve, int colorIndex );
diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.cpp b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.cpp
index 49142e9525..da224ae1cc 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.cpp
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.cpp
@@ -349,7 +349,7 @@ bool RimSummaryEnsembleTools::isEnsembleCurve( RimPlotCurve* sourceCurve )
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
-void RimSummaryEnsembleTools::highlightCurvesForSameRealization( RimPlotCurve* sourceCurve )
+void RimSummaryEnsembleTools::highlightCurvesForSameRealizationFromCurve( RimPlotCurve* sourceCurve )
 {
     auto sourceSummaryCurve = dynamic_cast<RimSummaryCurve*>( sourceCurve );
     if ( !sourceSummaryCurve ) return;
@@ -369,6 +369,16 @@ void RimSummaryEnsembleTools::highlightCurvesForSameRealization( RimPlotCurve* s
         }
     }
 
+    highlightCurvesForSameRealization( sourceCase );
+}
+
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+void RimSummaryEnsembleTools::highlightCurvesForSameRealization( RimSummaryCase* sourceCase )
+{
+    if ( !sourceCase ) return;
+
     auto summaryPlotColl = RiaSummaryTools::summaryMultiPlotCollection();
 
     for ( auto multiPlot : summaryPlotColl->multiPlots() )
diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.h b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.h
index 5974b668b4..442c5c65f9 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.h
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryEnsembleTools.h
@@ -39,7 +39,8 @@ std::vector<RigEnsembleParameter> createVariationSortedEnsembleParameters( const
 size_t calculateEnsembleParametersIntersectionHash( const std::vector<RimSummaryCase*>& summaryCases );
 
 bool isEnsembleCurve( RimPlotCurve* sourceCurve );
-void highlightCurvesForSameRealization( RimPlotCurve* sourceCurve );
+void highlightCurvesForSameRealizationFromCurve( RimPlotCurve* sourceCurve );
+void highlightCurvesForSameRealization( RimSummaryCase* sourceCase );
 void resetHighlightAllPlots();
 
 } // namespace RimSummaryEnsembleTools
diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryMultiPlot.cpp b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryMultiPlot.cpp
index 7db78b3ebe..3c771b0bf6 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryMultiPlot.cpp
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryMultiPlot.cpp
@@ -1760,23 +1760,44 @@ void RimSummaryMultiPlot::updateReadOutLines( double qwtTimeValue, double yValue
 
         if ( m_readOutSettings->enableHorizontalLine() )
         {
-            if ( auto leftAxisProperties = dynamic_cast<RimPlotAxisProperties*>( plot->axisPropertiesForPlotAxis( RiuPlotAxis::defaultLeft() ) ) )
-            {
-                leftAxisProperties->removeAllAnnotations();
+            std::vector<RimSummaryCurve*> summaryCurves;
 
-                auto summaryCurves = plot->summaryCurves();
-                if ( !summaryCurves.empty() )
+            // 1. Check if any curves are highlighted
+            if ( auto plotWidget = dynamic_cast<RiuQwtPlotWidget*>( plot->plotWidget() ) )
+            {
+                for ( auto highlightCurve : plotWidget->highlightedCurves() )
                 {
-                    auto firstCurve = summaryCurves.front();
-                    yValue          = firstCurve->yValueAtTimeT( timeTValue );
+                    if ( auto summaryCurve = dynamic_cast<RimSummaryCurve*>( highlightCurve ) )
+                    {
+                        summaryCurves.push_back( summaryCurve );
+                    }
                 }
+            }
+
+            // 2. If no curves are highlighted, use summary curves from single realizations
+            if ( summaryCurves.empty() )
+            {
+                summaryCurves = plot->summaryCurves();
+            }
+
+            auto annotationAxis = dynamic_cast<RimPlotAxisProperties*>( plot->axisPropertiesForPlotAxis( RiuPlotAxis::defaultLeft() ) );
+            if ( !summaryCurves.empty() )
+            {
+                auto firstCurve = summaryCurves.front();
+                yValue          = firstCurve->yValueAtTimeT( timeTValue );
+                annotationAxis  = dynamic_cast<RimPlotAxisProperties*>( plot->axisPropertiesForPlotAxis( firstCurve->axisY() ) );
+            }
+
+            if ( annotationAxis )
+            {
+                annotationAxis->removeAllAnnotations();
 
                 auto anno = new RimPlotAxisAnnotation();
                 anno->setAnnotationType( RimPlotAxisAnnotation::AnnotationType::LINE );
 
                 anno->setValue( yValue );
 
-                auto scaledValue = yValue / leftAxisProperties->scaleFactor();
+                auto scaledValue = yValue / annotationAxis->scaleFactor();
                 auto valueText   = RiaNumberFormat::valueToText( scaledValue, RiaNumberFormat::NumberFormatType::FIXED, 2 );
 
                 anno->setName( valueText );
@@ -1788,10 +1809,12 @@ void RimSummaryMultiPlot::updateReadOutLines( double qwtTimeValue, double yValue
                 anno->setColor( lineAppearance->color() );
                 anno->setAlignment( m_readOutSettings->horizontalLineLabelAlignment() );
 
-                leftAxisProperties->appendAnnotation( anno );
+                annotationAxis->appendAnnotation( anno );
             }
         }
 
-        plot->updateAxes();
+        // Calling plot->updateAxes() does not work for the first plot in a multiplot. Use fine grained update of annotation objects.
+        plot->updateAnnotationsInPlotWidget();
+        plot->updatePlotWidgetFromAxisRanges();
     }
 }
diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.cpp b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.cpp
index c13c5f2e91..0ae0ff122b 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.cpp
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.cpp
@@ -212,18 +212,7 @@ void RimSummaryPlot::updateAxes()
     updateNumericalAxis( RiaDefines::PlotAxis::PLOT_AXIS_LEFT );
     updateNumericalAxis( RiaDefines::PlotAxis::PLOT_AXIS_RIGHT );
 
-    if ( m_summaryPlot ) m_summaryPlot->clearAnnotationObjects();
-
-    if ( timeAxisProperties() && plotWidget() )
-    {
-        m_summaryPlot->updateAnnotationObjects( timeAxisProperties() );
-    }
-
-    RimPlotAxisPropertiesInterface* leftYAxisProperties = axisPropertiesForPlotAxis( RiuPlotAxis::defaultLeft() );
-    if ( leftYAxisProperties && plotWidget() )
-    {
-        m_summaryPlot->updateAnnotationObjects( leftYAxisProperties );
-    }
+    updateAnnotationsInPlotWidget();
 
     updateNumericalAxis( RiaDefines::PlotAxis::PLOT_AXIS_BOTTOM );
     updateNumericalAxis( RiaDefines::PlotAxis::PLOT_AXIS_TOP );
@@ -232,6 +221,26 @@ void RimSummaryPlot::updateAxes()
     updatePlotWidgetFromAxisRanges();
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+void RimSummaryPlot::updateAnnotationsInPlotWidget()
+{
+    if ( m_summaryPlot ) m_summaryPlot->clearAnnotationObjects();
+
+    if ( !plotWidget() ) return;
+
+    if ( timeAxisProperties() )
+    {
+        m_summaryPlot->updateAnnotationObjects( timeAxisProperties() );
+    }
+
+    if ( auto leftYAxisProperties = axisPropertiesForPlotAxis( RiuPlotAxis::defaultLeft() ) )
+    {
+        m_summaryPlot->updateAnnotationObjects( leftYAxisProperties );
+    }
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
diff --git a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.h b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.h
index d8543f4fb4..790f218976 100644
--- a/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.h
+++ b/ApplicationLibCode/ProjectDataModel/Summary/RimSummaryPlot.h
@@ -129,6 +129,7 @@ public:
     RimTimeAxisAnnotation* addTimeRangeAnnotation( time_t startTime, time_t endTime );
     void                   removeTimeAnnotation( RimTimeAxisAnnotation* annotation );
     void                   removeAllTimeAnnotations();
+    void                   updateAnnotationsInPlotWidget();
 
     void updateAxes() override;
 
diff --git a/ApplicationLibCode/UserInterface/RiuPlotAnnotationTool.cpp b/ApplicationLibCode/UserInterface/RiuPlotAnnotationTool.cpp
index d586508b6b..89cf05c9b4 100644
--- a/ApplicationLibCode/UserInterface/RiuPlotAnnotationTool.cpp
+++ b/ApplicationLibCode/UserInterface/RiuPlotAnnotationTool.cpp
@@ -20,6 +20,7 @@
 
 #include "RimPlotAxisAnnotation.h"
 #include "RiuGuiTheme.h"
+#include "RiuQwtPlotCurveDefines.h"
 
 #include "cafCategoryMapper.h"
 #include "cvfMath.h"
@@ -408,4 +409,6 @@ void RiuPlotAnnotationTool::setLineProperties( QwtPlotMarker*          line,
         line->setLineStyle( QwtPlotMarker::VLine );
         line->setXValue( linePosition );
     }
+
+    line->setZ( RiuQwtPlotCurveDefines::zDepthForIndex( RiuQwtPlotCurveDefines::ZIndex::Z_ANNOTATION ) );
 }
diff --git a/ApplicationLibCode/UserInterface/RiuPlotCurve.h b/ApplicationLibCode/UserInterface/RiuPlotCurve.h
index 5e55185ee7..5e7b491d1f 100644
--- a/ApplicationLibCode/UserInterface/RiuPlotCurve.h
+++ b/ApplicationLibCode/UserInterface/RiuPlotCurve.h
@@ -56,7 +56,6 @@ class RiuPlotCurve
 {
 public:
     explicit RiuPlotCurve( RimPlotCurve* ownerRimCurve, const QString& title = QString() );
-    explicit RiuPlotCurve();
     virtual ~RiuPlotCurve();
 
     virtual void setTitle( const QString& title ) = 0;
diff --git a/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp b/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp
index fab7c4bba0..c92417e830 100644
--- a/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp
+++ b/ApplicationLibCode/UserInterface/RiuPlotMainWindow.cpp
@@ -31,8 +31,10 @@
 #include "RimMainPlotCollection.h"
 #include "RimMultiPlot.h"
 #include "RimProject.h"
+#include "RimSummaryCase.h"
 #include "RimSummaryCaseMainCollection.h"
 #include "RimSummaryCurveCollection.h"
+#include "RimSummaryEnsembleTools.h"
 #include "RimSummaryMultiPlot.h"
 #include "RimSummaryMultiPlotCollection.h"
 #include "RimSummaryPlot.h"
@@ -942,6 +944,11 @@ void RiuPlotMainWindow::selectedObjectsChanged( caf::PdmUiTreeView* projectTree,
 
         if ( !firstSelectedObject ) return;
 
+        if ( auto summaryCase = dynamic_cast<RimSummaryCase*>( firstSelectedObject ) )
+        {
+            RimSummaryEnsembleTools::highlightCurvesForSameRealization( summaryCase );
+        }
+
         RimViewWindow* selectedWindow = dynamic_cast<RimViewWindow*>( firstSelectedObject );
         if ( !selectedWindow )
         {
diff --git a/ApplicationLibCode/UserInterface/RiuQwtCurvePointTracker.cpp b/ApplicationLibCode/UserInterface/RiuQwtCurvePointTracker.cpp
index ab57583754..ceed8c7331 100644
--- a/ApplicationLibCode/UserInterface/RiuQwtCurvePointTracker.cpp
+++ b/ApplicationLibCode/UserInterface/RiuQwtCurvePointTracker.cpp
@@ -19,6 +19,7 @@
 #include "RiuQwtCurvePointTracker.h"
 
 #include "RiaQDateTimeTools.h"
+
 #include "RiuGuiTheme.h"
 #include "RiuPlotCurve.h"
 #include "RiuPlotCurveInfoTextProvider.h"
@@ -45,9 +46,7 @@ RiuQwtCurvePointTracker::RiuQwtCurvePointTracker( QwtPlot* plot, bool isMainAxis
     setTrackerMode( QwtPicker::AlwaysOn );
     m_plotMarker = new QwtPlotMarker;
 
-    // Have this marker always on top of all curves/plot items.
-    double zAlwaysOnTop = 99999999;
-    m_plotMarker->setZ( zAlwaysOnTop );
+    m_plotMarker->setZ( RiuQwtPlotCurveDefines::zDepthForIndex( RiuQwtPlotCurveDefines::ZIndex::Z_ANNOTATION ) );
 
     auto color = RiuGuiTheme::getColorByVariableName( "markerColor" );
 
diff --git a/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.cpp b/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.cpp
index 46973d509d..5e1c0f4bf8 100644
--- a/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.cpp
+++ b/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.cpp
@@ -73,6 +73,9 @@ int RiuQwtPlotCurveDefines::zDepthForIndex( ZIndex index )
         case RiuQwtPlotCurveDefines::ZIndex::Z_REGRESSION_CURVE:
             return 700;
             break;
+        case RiuQwtPlotCurveDefines::ZIndex::Z_ANNOTATION:
+            return 9999;
+            break;
 
         default:
             break;
diff --git a/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.h b/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.h
index 2a92f2acea..0adf441b98 100644
--- a/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.h
+++ b/ApplicationLibCode/UserInterface/RiuQwtPlotCurveDefines.h
@@ -47,7 +47,8 @@ enum class ZIndex
     Z_ERROR_BARS,
     Z_SINGLE_CURVE_OBSERVED,
     Z_PLOT_RECT_ANNOTATION,
-    Z_REGRESSION_CURVE
+    Z_REGRESSION_CURVE,
+    Z_ANNOTATION
 };
 
 int zDepthForIndex( ZIndex index );
diff --git a/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.cpp b/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.cpp
index 203b17c0dd..45b68f3c53 100644
--- a/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.cpp
+++ b/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.cpp
@@ -942,7 +942,7 @@ void RiuQwtPlotWidget::selectClosestPlotItem( const QPoint& pos, bool toggleItem
             const auto rimCurve = curve->ownerRimCurve();
             if ( RimSummaryEnsembleTools::isEnsembleCurve( rimCurve ) )
             {
-                RimSummaryEnsembleTools::highlightCurvesForSameRealization( rimCurve );
+                RimSummaryEnsembleTools::highlightCurvesForSameRealizationFromCurve( rimCurve );
             }
             else
             {
@@ -1055,6 +1055,8 @@ void RiuQwtPlotWidget::highlightPlotCurves( const std::set<RimPlotCurve*>& curve
                 plotCurve->setPen( existingPen );
                 plotCurve->setZ( zValue + 100.0 );
                 highlightPlotAxes( plotCurve->xAxis(), plotCurve->yAxis() );
+
+                m_hightlightedCurves.push_back( currentRimPlotCurve );
             }
             else
             {
@@ -1110,11 +1112,21 @@ void RiuQwtPlotWidget::resetPlotItemHighlighting( bool doUpdateCurveOrder )
     if ( doUpdateCurveOrder ) updateCurveOrder();
 }
 
+//--------------------------------------------------------------------------------------------------
+///
+//--------------------------------------------------------------------------------------------------
+std::vector<RimPlotCurve*> RiuQwtPlotWidget::highlightedCurves() const
+{
+    return m_hightlightedCurves;
+}
+
 //--------------------------------------------------------------------------------------------------
 ///
 //--------------------------------------------------------------------------------------------------
 void RiuQwtPlotWidget::resetPlotCurveHighlighting()
 {
+    m_hightlightedCurves.clear();
+
     if ( !m_plotDefinition || m_originalZValues.empty() )
     {
         return;
diff --git a/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.h b/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.h
index 728445cbdc..ddbb7cc57f 100644
--- a/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.h
+++ b/ApplicationLibCode/UserInterface/RiuQwtPlotWidget.h
@@ -164,9 +164,10 @@ public:
 
     QwtAxisId toQwtPlotAxis( RiuPlotAxis axis ) const;
 
-    void highlightPlotItem( const QwtPlotItem* plotItem );
-    void highlightCurvesUpdateOrder( const std::set<RimPlotCurve*>& curves );
-    void resetPlotItemHighlighting( bool doUpdateCurveOrder = true );
+    void                       highlightPlotItem( const QwtPlotItem* plotItem );
+    void                       highlightCurvesUpdateOrder( const std::set<RimPlotCurve*>& curves );
+    void                       resetPlotItemHighlighting( bool doUpdateCurveOrder = true );
+    std::vector<RimPlotCurve*> highlightedCurves() const;
 
     void replot() override;
 
@@ -231,6 +232,7 @@ private:
     };
 
     std::map<QwtPlotCurve*, double>  m_originalZValues;
+    std::vector<RimPlotCurve*>       m_hightlightedCurves;
     std::map<RiuPlotAxis, QwtAxisId> m_axisMapping;
 
     QPointer<QwtPlot> m_plot;