The TARDIS lands on Earth circa 40000 BC. The Doctor and Turlough head for a rise in terrain, below which they can see a tribe of Cro-Magnons. The Doctor hopes to observe the first contact between Neanderthals and Cro-Magnons. He has spent much research into finding the correct moment, and has narrowed it down within six months. Turlough is amazed at the prospect of observing for six months. The Doctor suggests he take the TARDIS and jump ahead six months so he won't have to wait with the Doctor. As Turlough heads back to the TARDIS, the Doctor sets up his surveillance equipment.
Turlough sets the TARDIS controls and materialises six months later. He heads for the Doctor's site and realises something is wrong. The Doctor is impatient with Turlough and tells him to gather the rest of the equipment while he heads for the TARDIS. As Turlough picks up the equipment, he finds the Doctor's notebook. He furtively reads it while he packs.
- After more than three weeks of watching the Cro-Magnons, the Doctor notes the Neanderthals' arrival. For almost four months, the two tribes go about their business, not meeting at all. After six months, expecting Turlough any day, the Doctor scouts around his observation site and finds something unexpected. He notes the coordinates in the notebook.
Turlough, curious, heads for the location specified by the coordinates. He finds a dead Neanderthal body and deduces that the man had seen the Doctor's camp site and died while approaching it. Turlough sees a Neanderthal approach, but he retreats when he sees that Turlough has seen him. Turlough heads back to the TARDIS.
The last thing Turlough sees is members from both tribes approaching the spot.
- Turlough is capable of operating the TARDIS with enough accuracy to move it forward in time six months so that he can collect the Doctor.
- Turlough thinks the Doctor is going to play cricket because he is carrying the kind of bag cricketers use for their bats.
- The term "psychologico-human" was first coined in the late 21st century by Professor Dorkus Merriman, though it was not added to the Oxford English Dictionary until 2107. The Doctor claims to have been with Merriman at the time he thought the word up.
- This story is narrated by Turlough.
to be added