diff --git a/api/plugin.go b/api/plugin.go
index b0b3e21..97f0a35 100644
--- a/api/plugin.go
+++ b/api/plugin.go
@@ -23,13 +23,23 @@ type PluginInfo struct {
 	Retry *Retry
 }
 
+type DefaultsHandler interface {
+	yaml.Unmarshaler
+	// Merge merges the supplies map of key/value combinations with the set of
+	// handled defaults for the plugin. The supplied key/value map will NOT be
+	// unpacked from its top-most plugin named element. So, for example, the
+	// kube plugin should expect to get a map that looks like
+	// "kube:namespace:<namespace>" and not "namespace:<namespace>".
+	Merge(map[string]any)
+}
+
 // Plugin is the driver interface for different types of gdt tests.
 type Plugin interface {
 	// Info returns a struct that describes what the plugin does
 	Info() PluginInfo
 	// Defaults returns a YAML Unmarshaler types that the plugin knows how
 	// to parse its defaults configuration with.
-	Defaults() yaml.Unmarshaler
+	Defaults() DefaultsHandler
 	// Specs returns a list of YAML Unmarshaler types that the plugin knows
 	// how to parse.
 	Specs() []Evaluable
diff --git a/context/context_test.go b/context/context_test.go
index 5d41973..2b2ed3d 100644
--- a/context/context_test.go
+++ b/context/context_test.go
@@ -21,6 +21,8 @@ type fooDefaults struct {
 	Foo string `yaml:"foo"`
 }
 
+func (d *fooDefaults) Merge(map[string]any) {}
+
 func (d *fooDefaults) UnmarshalYAML(node *yaml.Node) error {
 	return nil
 }
@@ -62,7 +64,7 @@ func (p *fooPlugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *fooPlugin) Defaults() yaml.Unmarshaler {
+func (p *fooPlugin) Defaults() api.DefaultsHandler {
 	return &fooDefaults{}
 }
 
diff --git a/internal/testutil/plugin/bar/plugin.go b/internal/testutil/plugin/bar/plugin.go
index 4f2774b..2dda4a0 100644
--- a/internal/testutil/plugin/bar/plugin.go
+++ b/internal/testutil/plugin/bar/plugin.go
@@ -28,6 +28,8 @@ type Defaults struct {
 	Foo string `yaml:"bar"`
 }
 
+func (d *Defaults) Merge(map[string]any) {}
+
 func (d *Defaults) UnmarshalYAML(node *yaml.Node) error {
 	return nil
 }
@@ -98,7 +100,7 @@ func (p *Plugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *Plugin) Defaults() yaml.Unmarshaler {
+func (p *Plugin) Defaults() api.DefaultsHandler {
 	return &Defaults{}
 }
 
diff --git a/internal/testutil/plugin/failer/plugin.go b/internal/testutil/plugin/failer/plugin.go
index 043e651..913ecee 100644
--- a/internal/testutil/plugin/failer/plugin.go
+++ b/internal/testutil/plugin/failer/plugin.go
@@ -28,6 +28,8 @@ type Defaults struct {
 	InnerDefaults
 }
 
+func (d *Defaults) Merge(map[string]any) {}
+
 func (d *Defaults) UnmarshalYAML(node *yaml.Node) error {
 	if node.Kind != yaml.MappingNode {
 		return parse.ExpectedMapAt(node)
@@ -129,7 +131,7 @@ func (p *Plugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *Plugin) Defaults() yaml.Unmarshaler {
+func (p *Plugin) Defaults() api.DefaultsHandler {
 	return &Defaults{}
 }
 
diff --git a/internal/testutil/plugin/foo/plugin.go b/internal/testutil/plugin/foo/plugin.go
index d8eb5e9..9b640a3 100644
--- a/internal/testutil/plugin/foo/plugin.go
+++ b/internal/testutil/plugin/foo/plugin.go
@@ -33,6 +33,8 @@ type Defaults struct {
 	InnerDefaults `yaml:",inline"`
 }
 
+func (d *Defaults) Merge(map[string]any) {}
+
 func (d *Defaults) UnmarshalYAML(node *yaml.Node) error {
 	if node.Kind != yaml.MappingNode {
 		return parse.ExpectedMapAt(node)
@@ -136,7 +138,7 @@ func (p *Plugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *Plugin) Defaults() yaml.Unmarshaler {
+func (p *Plugin) Defaults() api.DefaultsHandler {
 	return &Defaults{}
 }
 
diff --git a/internal/testutil/plugin/priorrun/plugin.go b/internal/testutil/plugin/priorrun/plugin.go
index 58c279a..dd2a070 100644
--- a/internal/testutil/plugin/priorrun/plugin.go
+++ b/internal/testutil/plugin/priorrun/plugin.go
@@ -24,6 +24,8 @@ const PriorRunDataKey = "priorrun"
 
 type Defaults struct{}
 
+func (d *Defaults) Merge(map[string]any) {}
+
 func (d *Defaults) UnmarshalYAML(node *yaml.Node) error {
 	return nil
 }
@@ -116,7 +118,7 @@ func (p *Plugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *Plugin) Defaults() yaml.Unmarshaler {
+func (p *Plugin) Defaults() api.DefaultsHandler {
 	return &Defaults{}
 }
 
diff --git a/plugin/exec/defaults.go b/plugin/exec/defaults.go
index 6355a0b..d96ee1a 100644
--- a/plugin/exec/defaults.go
+++ b/plugin/exec/defaults.go
@@ -16,6 +16,13 @@ type Defaults struct {
 	execDefaults
 }
 
+// Merge merges the supplies map of key/value combinations with the set of
+// handled defaults for the plugin. The supplied key/value map will NOT be
+// unpacked from its top-most plugin named element. So, for example, the
+// kube plugin should expect to get a map that looks like
+// "kube:namespace:<namespace>" and not "namespace:<namespace>".
+func (d *Defaults) Merge(map[string]any) {}
+
 func (d *Defaults) UnmarshalYAML(node *yaml.Node) error {
 	if node.Kind != yaml.MappingNode {
 		return parse.ExpectedMapAt(node)
diff --git a/plugin/exec/plugin.go b/plugin/exec/plugin.go
index ac1ac14..0a06230 100644
--- a/plugin/exec/plugin.go
+++ b/plugin/exec/plugin.go
@@ -5,8 +5,6 @@
 package exec
 
 import (
-	"gopkg.in/yaml.v3"
-
 	"github.com/gdt-dev/core/api"
 	gdtplugin "github.com/gdt-dev/core/plugin"
 )
@@ -44,7 +42,7 @@ func (p *plugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *plugin) Defaults() yaml.Unmarshaler {
+func (p *plugin) Defaults() api.DefaultsHandler {
 	return &Defaults{}
 }
 
diff --git a/plugin/registry_test.go b/plugin/registry_test.go
index f03d6a3..9c2f35f 100644
--- a/plugin/registry_test.go
+++ b/plugin/registry_test.go
@@ -18,6 +18,8 @@ type fooDefaults struct {
 	Foo string `yaml:"foo"`
 }
 
+func (d *fooDefaults) Merge(map[string]any) {}
+
 func (d *fooDefaults) UnmarshalYAML(node *yaml.Node) error {
 	return nil
 }
@@ -59,7 +61,7 @@ func (p *fooPlugin) Info() api.PluginInfo {
 	}
 }
 
-func (p *fooPlugin) Defaults() yaml.Unmarshaler {
+func (p *fooPlugin) Defaults() api.DefaultsHandler {
 	return &fooDefaults{}
 }
 
diff --git a/scenario/parse.go b/scenario/parse.go
index 1c9e52d..8f4e220 100644
--- a/scenario/parse.go
+++ b/scenario/parse.go
@@ -81,6 +81,10 @@ func (s *Scenario) UnmarshalYAML(node *yaml.Node) error {
 				if err := valNode.Decode(plugDefaults); err != nil {
 					return err
 				}
+				// The user may have used scenario.WithDefaults() so we need to
+				// merge anything we got from WithDefaults with anything we
+				// parsed from the plugins.
+				plugDefaults.Merge(s.Defaults)
 				defaults[p.Info().Name] = plugDefaults
 			}
 			// The scenario may have its own defaults as well, so we stash