A mix tape from 1983 is discovered, containing the voice of a teenage girl who was murdered shortly after it went into her school's time capsule. Griffin becomes convinced that the girl is reading from a speech secretly prepared for the Queen to broadcast in the event of a nuclear war.

Meanwhile Sasha is distracted by a romantic entanglement with a charming record shop owner and Gerry is dreading his future son-in-law Robin's stag night, which promises to be something very special...