Anna and Michael are stranded in the desert without any water. Pell isn't far behind. Will he find them in time?
Saved from 'termination' by the aliens known as the Nirikarr, Anna and Michael agree to keep their existence secret and, with three days leave, go to Earth for Christmas. If they are not back in three days, their lives could be forfeit.
Then Nelli, their Nirikarr friend, shows up to warn them of impending danger. But it's too late, all three are captured and wake up in a desert: sand and camels and people in blue robes. How will they survive? It's only dawn, the heat is oppressive, and they haven't even got any water.
But this isn't Earth, it is Anna's world where the Nirikarr also live. But Nelli tells them her home is beyond the equator across an uncrossable desert. To attempt it is to risk agonising death from ultraviolet radiation. And they don't know that a cut-throat, intent on killing them, is close behind disguised as a camel driver. He follows them into the burning heart of the desert.
But what is happening in Siberia? Something crashed at Tunguska in 1808. Whatever it was they are ready now to pour out of their lair and claim the Earth for themselves.