A prison cell. Four prisoners. There's Carrère, a young company director charged with fraud, Marcus, 35, a transsexual mid-way through metamorphosis, Pâquerette, 20, mentally handicapped and Lassalle, 60, an intellectual, locked up for murdering his wife. Hidden behind a stone in the cell wall that has mysteriously come loose, they discover a book: the diary of a prisoner, Danvers, who had occupied the cell at the beginning of the century. In this diary are revealed magical formulas that hold the secret of escape... But since they discovered the book, the inmates witness more and more strange and disturbing occurrences in the cell...