River Song is alone in a small abandoned space station orbiting a dying star. She has just come back from a mission where she was badly injured. Her body is about to give out, and she knows that regeneration is necessary. However, this time, something is different: alien technology on the station is interfering with her regeneration process. Her body begins to split into two distinct forms.

Instead of a classic regeneration, River feels her energy split into two parallel streams, she Bi-Regenerating.