The Nightmare Game — Gillian Cross

The thrilling conclusion of a groundbreaking trilogy has arrived. Robert journeyed through a strange parallel world with the help of a tiny band of fellow survivors. Now home, Robert, with his best friend, Tom, and sister, Emma, are desperate to save the others before winter sets in and cold destroys their fragile existence. But the three friends discover a sinister connection between their own and the parallel world?a darkness that will test their courage, their friendship, and their hope for the future.
Seamlessly blending fantasy with a hard-hitting tale of love and survival, Gillian Cross weaves the final tale in a startlingly original, spellbinding series.