Unnatural History

In London, a young woman named Sam works in a shop when the Doctor arrives and tells her she should have blonde hair and be traveling with him. When she runs out onto the street, she is attacked by a ten-year-old boy who claims she shouldn't exist. The Doctor rescues her and takes her to San Francisco, where he and his companion Fitz discover that a rift in space-time is drawing dangerous creatures from other dimensions. The TARDIS is trapped inside the rift and will be destroyed in three days unless it is removed. The Doctor must close the rift before it is too late.