Sergeant Kandula is running away when he runs into the Doctor. Kandula's superiors think he has captured the Doctor, who is taken to their camp. There, Kandula explains that they are looking for their Tipping Device, which collided with 24th century Prague. The Crei have taken Prague out of time to search for their device, which they claim will help to end a war.
The Doctor, in order to prevent the Crei from destroying Prague (and to get his TARDIS back), offers to help them. The Tipping Device contains one atom of gold, so the Doctor and Kandula search through various artefacts of Prague, with no success.
The Doctor, thanks to hints from Kandula, realises the Crei plan to use the Tipping Device to destroy their enemies. The Doctor and Kandula run for the TARDIS, chased by the Crei, and Kandula is shot.
Inside the TARDIS, Kandula reveals that he had placed the device in the Doctor's pocket the moment they ran into each other. Kandula dies, knowing he kept the device from his superiors. Prague is returned to its rightful place, and the Doctor takes Kandula's body, along with the device, to the end of the universe and leaves it in space.
- The Crei's government is called the Crei Imperative.
- The Doctor quotes architect Josef Gočár and says he's met Tycho Brahe.
- Among the landmarks visited are the Old Town Square, the Jan Hus Memorial, the Old Jewish Cemetery, the Charles Bridge, the Crucifix and Calvary, the Statue of the Holy Savior with Cosmas and Damian, the Church of Our Lady before Týn, the Astronomical Clock, and the House of the Black Madonna.
- This story was reprinted in Short Trips: Re:Collections.