 It is the second of a two-part story; the first part, "Silence in the Library", aired on 31 May.In the episode, the time-travelling temp Donna Noble (Catherine Tate) is trapped inside a virtual reality in a planet-sized library's hard drive in the 51st century and has false memories implanted of a married life.At the same time, another time traveller, the Tenth Doctor (David Tennant), seeks to rescue Donna, and thousands of other humans saved inside the library hard drive while being pursued by the microscopic swarm called Vashta Nerada.