Mark and Steph are struggling to move on with their lives after armed robbers broke into their home and brutalized them. Shaken, they decide to get away and leave their troubles behind. A house swap in Paris with a couple they meet online, the Petits, seems to provide the perfect escape. But upon arriving for a week's luxurious break, they find themselves in a festering, run-down apartment. And when Steph attempts to contact the Petits, she gets no answer.

Mark and Steph try to make the most of the trip, but they are unable to relax. After a series of increasingly unsettling events, they decide to return home. Yet when they arrive, neither of them can shake the feeling that there's now something sinister about their own house. As time passes, Mark is terrorized by a series of unsettling visions. But is it all in his imagination or is there a far more worrying explanation . . . ?

Praise for S. L. Grey's Under Ground

'Under Ground shifts from slow-burn chills to its frantic finale with considerable expertise. A gripping book - and definitely not for the claustrophobic' SFX

'It's J. G. Ballard meets Agatha Christie, with a soupcon of Patricia Highsmith thrown in' Guardian

'Cramped, claustrophobic and menacing, with a climax that kicks the stuffing out of you' Independent