Frankfurt police inspector Birke is under pressure from his boss - he's got only one night - to extract a confession from the alleged cop killer Ernst. The suspect has an alibi: he says he was with society lady Isabel Wellingsen. Though it's unlikely, Birke has to check the alibi and proceeds to interrogate the surprisingly cooperative Isabel. It is a night-long confrontation of two highly different personalities, each of whom is determined to win the duel in the night ...