The Fifth Doctor investigates the Vault of Stellar Curios, where he has observed evidence of time leakage. But then the Daleks attack, looking for the contents of the mysterious vault. The Eighth Doctor also shows up and he and his former self create a time loop trap, spanning between their lives. This sends the Daleks to the Seventh Doctor's encounter with Michael Faraday in 1854 and the Sixth Doctor's visit to an early Dalek battlefield.