The TARDIS materialises on Culloden Moor just after the rout of the Jacobite rebels in 1745. The British army is mopping up survivors, and when they find the Doctor and Ben in the company of rebels they are accused of desertion and arrested. They are saved from execution by Solicitor Grey, the Commissioner of Prisons – but he has his own agenda for the prisoners. Imprisoned in Inverness, the Doctor realises that Grey is running a scam of his own, removing rebels from the prisons with the promise that they will be saved from execution if they sign contracts binding them to service in the Jamaican plantations. In short, he's a slave trader. While the Doctor and Ben try to find a way to escape and help their new friends, Polly and Kirsty MacLaren, whose father has been kidnapped by Grey, blackmail an English officer into helping them locate their kidnapped friends and family. The Doctor and his companions must then find their way back to the TARDIS through a battlefield, and the young Highland piper who helps them, Jamie McCrimmon, accompanies them on their travels.