Carvalho is investigating the murder of a prison officer. The police suspect a young delinquent who had threatened to kill the officer. But Carvalho and Biscuter are on the trail of a friend and ex-cell partner of the defendant called "el Navajas" ("the penknife"). He is a pusher in the discotheque Up & Down. Things get worse when "el Navajas" turns out to be the main suspect of the murder in cold blood of a boy from a good family in the discotheque. Carvalho must find the pusher before the police in order to avoid that his client is sentenced to life imprisonment.