Detailed Instructions: Given a premise, an initial context, an original ending, and a counterfactual context, the task is to generate a new story ending aligned with the counterfactual context and as close to the original ending as possible. Each instance consists of a five-sentence story. The premise is the first sentence of a story, and the second sentence, which is the initial context, provides more information about the story's context and the story's general plot. The original ending is the last three sentences of the story. Also, a counterfactual context is a slight modification to the initial context. You should write a new story ending that edits the original story ending as little as possible to regain coherence with the counterfactual context. To sum up, you should write the last three sentences of a story based on the premise(first sentence) and the counterfactual context(second sentence) of the story.
Q: Premise: Edgar loved his family's mastiffs, but he wished for a horse. 
 Initial Context: He even wrote to Santa Claus asking for a horse ride for Christmas! 
 Original Ending: Edgar's dad had an idea for making that wish come true. On Christmas morning he set little Edgar on the largest dog. The dog let Edgar ride him just like a real horse! 
 Counterfactual Context: He even wrote to his Grandmother asking for a horse for his birthday.
A:
Edgar's grandmother had an idea for making that wish come true. On Christmas morning she set little Edgar on the largest dog. The dog let Edgar ride him just like a real horse! 