The plot follows a private detective, an ex communist and former CIA agent, who travels from Barcelona to Madrid to discover the identity of the assassin of the leader of the Spanish Communist party who was stabbed during a blackout while presiding over a meeting of the party's central committee. The film is a thriller with ironic political overtones.

In a western and Mediterranean country, very fond of bullfighting and soccer, legislative elections are held, that is, "El Gran Mogollón" is elected from the bosses. Each leader feels that his position is secure, and some are preparing to take the presidency of "El Gran Mogollón", when the surprise arises: the P.E.R. has won by a wide margin.