Two young boys, Coyn and Shalin, are making a model of their people's Great Temple out of pebbles. Their temple is disturbed by a gull, so they decide to catch one to sacrifice. Once they are finished, they decide to build a life-size, stone version of the Great Temple.
Several years later, Coyn is the leader of the Bear Men, and Shalin is the magic-maker. They are in the middle of constructing their temple. They have conquered a nearby tribe, who are led by Dorlan, to use as slave labour in constructing the temple. One wet night, they are hurrying to raise a large stone, trying to keep Coyn's schedule. The stone slips and kills a slave girl, Marin, best friend of Dorlan's sister Saffen. Coyn wants someone to blame and decides to sacrifice Dorlan.
As Dorlan is prepared for the sacrifice, the Doctor and Sam arrive nearby. Sam wanted to see Stonehenge, but the Doctor miscalculated the time, and they arrive in time to hear Dorlan scream. They separate and rush to the temple. Sam tries to bluff her way in, but the Bear Men and slaves are soon distracted by the Doctor's fireworks. Sam rescues Dorlan and takes him to the TARDIS to fix his broken arm. The Doctor is brought to Shalin.
Coyn wants Shalin to kill the Doctor, but Shalin can see that the Doctor is special and powerful. Shalin wants the Doctor to kill Coyn, who he feels is insane. Shalin doesn't realise that Coyn knows what he wants to do, and Coyn kills Shalin.
Meanwhile in the TARDIS, Sam fixes Dorlan's arm, and plans with him to use spray paint graffiti to scare the Bear Men. She warns Dorlan that it is dangerous to spray the paint in someone's eyes.
The Doctor has a long talk with Coyn, helping him see that it was wrong to kill his old friend. He convinces Coyn to let Dorlan's people go.
However, Dorlan has taken the spray paint and used it on the Bear Man guarding the TARDIS. He takes it to the temple, thinking it is a weapon to be used against the Bear Men. A fight ensues between the Bear Men and Dorlan's people, and Dorlan's uncle Teln is killed.
Coyn ends the fighting. Sam takes responsibility for starting the rebellion, and as punishment must help the women prepare the dead bodies for ceremony. Coyn frees Dorlan's people, and the Doctor and Sam leave in the TARDIS. The Doctor offers to take Sam back to Stonehenge, ten or twenty years later, and she says she'll think about it.
- Sam wants the Doctor to take her to see Stonehenge.
- The Doctor name-drops Emperors Caligula and Hadrian, but Sam stops him before he can name-drop Henry James.
to be added