In the last days of thetwenty-first century, sea creatures swim through the ruins of London. Trappedin the abyss, humankind wavers between fear and hope-fear of what lurks in thedepths around them, and hope that they might one day find a way back to thesurface.

When sixteen-year-oldsubmersible racer Leyla McQueen is chosen to participate in the city's prestigious annual marathon, she sees an opportunity to save her father, whohas been arrested on false charges. The Prime Minister promises the championwhatever their heart desires. But the race takes an unexpected turn, forcingLeyla to make an impossible choice.

Now she must braveunfathomable waters and defy a corrupt government determined to keep itssecrets, all the while dealing with a guarded, hotheaded companion she neverasked for in the first place. If Leyla fails to discover the truths at theheart of her world, or falls prey to her own fears, she risks capture-or worse.And her father will be lost to her forever.