It's Rory William's stag night and his friends have clubbed together to buy him a stripper in a cake present but The Doctor breaks out of it and ruins it. The Doctor tells Rory he's needed and takes him to see Amy Pond. He tells them that for a wedding present, he'll take them anywhere time or space that they'd like to go. As they don't give an answer, he takes them to Venice, 1580.
A young woman named Isabella is take before Signora Rosanna Calvierri to gain entry to a school for gifted. The woman is accepted in front of her father Guido. When Guido leaves, the other people in the hall crowd round her.
Amy and Rory see the young woman being carted off against her will and decide to investigate. Rory and Amy dress up in clothing of the time and pretend to be brother and sister from Sweden to get a meeting with Rosanna. Amy is accepted into the training,
Amy is taken to the tower and forced into a chair where when Rosanna comes close, Amy kicks Rosanna and the perception device is broken for a moment. Rosanna reveals her to be a giant lobster with a fish head. The aliens get back down to business and bite Amy's neck leaving two bite marks. Amy is rescued by Isabella who helps her to escape but when Amy runs outside, Isabella is unable to as she is now allergic to the Sunlight and captured by the vampires. Isabella is thrown into the water to be eaten.
The Doctor confronts Rosanna in her grand chamber. The Doctor recognises them as being from Saturnyne and that they are a race of vampiric like creatures called "Sisters of the Water". Rosanna saw Earth after seeing the crack in the universe and so came here to convert the people into her kind. The Doctor leaves to group up with Guido, Rory and Amy at Guido's home. The converted females turn up at Guido's home. The humans (inc. Doctor) make a run for it, Guido decides to stay behind and blow up his home and kill the Vampires to give the others a chance to escape.
Amy and Rory confront Francisco, Rosanna's son, the Doctor climbs the a building with loud bells to stop the weather. The Doctor climbs outside the tower to the very top and stop the machine at the top by flicking the switch. The Sisters had planned to sink Venice so that the place could be where the Sisters of the Water could live. Rosanna had targetted the women folk for mates for Rosanna's sons who lived under water. The converted women walked round in white nightgown showing off their ample cleavage.
The Doctor confronts Isbella but she doesn't want to know and jumps into the waters in Venice. Rosanna leaves the Doctor with a warning about "The Silence".