One of the Usborne Thrillers. Paul goes to a hypnotist to gain self-confidence from his domineering father and agrees to be part of an experiment into reincarnation. Unbeknownst to him, the lost spirit of Martin enters his body and takes over, forcing Peter to help him track down his dead girlfriend Helen’s spirit (which then enters a school friend’s body) and the 4(?) set off to find where Martin is buried. Hard to explain but easy to read.p.18 -24 Peter in “Dr” Black’s office discussing why he came and the reincarnation theory.