diff --git a/lib/mutant.rb b/lib/mutant.rb
index 2730dacb..61b295f9 100644
--- a/lib/mutant.rb
+++ b/lib/mutant.rb
@@ -39,6 +39,7 @@ require 'mutant/support/method_object'
 
 require 'mutant/random'
 require 'mutant/mutator'
+require 'mutant/mutation'
 require 'mutant/mutator/registry'
 require 'mutant/mutator/literal'
 require 'mutant/mutator/literal/boolean'
diff --git a/lib/mutant/mutation.rb b/lib/mutant/mutation.rb
new file mode 100644
index 00000000..4176624f
--- /dev/null
+++ b/lib/mutant/mutation.rb
@@ -0,0 +1,85 @@
+module Mutant
+  # Represent a mutated node with its subject
+  class Mutation
+    include Immutable
+
+    # Return mutated root node
+    #
+    # @return [Rubinius::AST::Script]
+    #
+    # @api private
+    #
+    def root
+      @subject.root(@node)
+    end
+    memoize :root
+
+    # Insert mutated node
+    #
+    # @return [self]
+    #
+    # @api private
+    #
+    def insert
+      Loader.run(root)
+      self
+    end
+
+    # Return identification
+    #
+    # @return [String]
+    #
+    # @api private
+    #
+    def identification
+      "#{@subject.identification}:#{sha1[0..4]}"
+    end
+
+    # Return sha1 sum of source
+    #
+    # @return [String]
+    #
+    # @api private
+    #
+    def sha1
+      SHA1.hexdigest(source)
+    end
+    memoize :sha1
+
+    # Return source
+    #
+    # @return [String]
+    #
+    # @api private
+    #
+    def source
+      @node.to_source
+    end
+    memoize :source
+
+    # Return original source
+    #
+    # @return [String]
+    #
+    # @api private
+    #
+    def original_source
+      @subject.source
+    end
+
+  private
+
+    # Initialize mutation object
+    #
+    # @param [Subject] subject
+    # @param [Rubinius::Node::AST] node
+    #
+    # @return [undefined]
+    #
+    # @api private
+    #
+    def initialize(subject, node)
+      @subject, @node = subject, node
+    end
+  end
+end