After librarian Ellen Barker is murdered investigating officer Grace Mackie contacts Danny, who had been in the same amateur sleuthing group as the dead woman. He suspects that Ellen was working on an old case but had come too close to the truth and been silenced. He works out that Ellen was trying to reopen the murder of Sally Tunstall, for which Barbara Haynes' son, now dead, was convicted. Danny and Nathan Wicks (fellow ex-cop and group member), visit Barbara and her neighbour Caroline Tate who, with her former husband Gabriel John Stokes and Sally, was a member of a commune. Stokes, now a government minister, confesses to an affair with Sally that destroyed his marriage and admits that Ellen visited him but left unharmed. When Nathan admits that he was infatuated with Ellen he is arrested but Danny follows another line to expose the double killer.