When fifteen-year-old Ty, who has always lived on the ocean floor, joins Topside girl Gemma in the frontier's underworld to seek and stop outlaws who threaten his home, they learn that the government may pose an even greater threat.

Ty discovers an entire township chained to a sunken submarine, its inhabitants condemned to an icy underwater grave. It's only the first clue to a mystery that has claimed hundreds of lives and stands to claim two more, lives very precious to Ty and his Topsider ally, Gemma.

In a post-apocalyptic future, teenaged Leyla feels compelled to search for Ari, while seeking to uncover the mystery behind her past. Leyla McQueen rescued her father from Broadmoor, the illegal government prison-- but his freedom comes at a terrible cost. She is separated from Ari, the boy who has her heart. Across Britain, the fallout from Leyla's actions has escalated tensions between Anthropoid and non-Anthropoid communities. In uncovering the...