 In the episode, alien time traveller the Doctor (Matt Smith) takes his companions Amy Pond (Karen Gillan) and her husband Rory (Arthur Darvill) to the planet Apalapucia for a holiday, but they find that the planet is on quarantine as the two-hearted natives are susceptible to a deadly plague.Amy accidentally gets separated from the Doctor and Rory but when they try to rescue her they arrive 36 years later in her timeline.The older Amy does not trust the Doctor, who is forced to remain on the TARDIS as he also has two hearts, and will not allow the Doctor and Rory to leave and rescue her at the correct point in her timeline.