Task: Story Composition
Input (English): Premise: Bob walked down the hall in the building where he worked. 
 Initial Context: His friend Joe came around the corner and walked with Bob. 
 Original Ending: They didn't say anything to each other. Once they had a large hall in front of then, Bob gave a nod. On cue, Bob and Joe began a foot race to the end of the hall. 
 Counterfactual Context: His friend Chelsea came around the corner and walked with Bob.
Output (English): They didn't say anything to each other. Once they had a large hall in front of then, Bob gave a nod. On cue, Bob and Chelsea began a foot race to the end of the hall.