"You're tinkering with time. That's always a bad idea unless you know what you're doing."

The Doctor takes Romana for a holiday in Paris – a city which, like a fine wine, has a bouquet all its own. Especially if you visit during one of the vintage years. But the TARDIS takes them to 1979, a table-wine year, a year whose vintage is soured by cracks – not in their wine glasses but in the very fabric of time itself.

Soon the Time Lords are embroiled in an audacious alien scheme which encompasses home-made time machines, the theft of the Mona Lisa, the resurrection of the much-feared Jagaroth race, and the beginning (and quite possibly the end) of all life on Earth.

Aided by British private detective Duggan, whose speciality is thumping people, the Doctor and Romana must thwart the machinations of the suave, mysterious Count Scarlioni – all twelve of him – if the human race has any chance of survival.

But then, the Doctor's holidays tend to turn out a bit like this.