Tracks: Series 3 and 4

Tracks: Chimera. A tower block collapses in London. Hundreds are killed. Except a man standing alone on the roof, who walks out of the rubble unscathed. And things are about to get stranger, because Dr Helen Ash is pregnant. But she hasn't had sex since her husband died 18 months ago. What connects her unexplained pregnancy, a mysterious phone message from a woman who died in the building collapse, and the man on the roof of the high-rise?

Tracks: Indigo. Dr Helen Ash is involved in a road accident. But where was she going in such a hurry? And why can't she remember? The answer lies in the riddle of Helen's daughter, Frances, who's older than she should be. And a mysterious 'child-mother', who's younger than she should be...