A hot summer in the early sixties. 16 year-old Simon wants to become popular with the immensely wealthy brothers Arnout and Victor van Riebeeck. On the capital estate where the two brothers live, the boys spend their time playing tennis, listening to music and dancing with Arnout's beautiful girlfriend Frederique. Meanwhile, in the attic of the villa they keep their friend Ronnie hidden. Ronnie is a petty criminal who is on the run for the police. Without neither the boys' parents nor the villa staff noticing anything, Ronnie is offered refuge at the villa. In the beginning the boys think the whole situation is funny, until Ronnie becomes a burden and he even starts to blackmail them. Only they don't dare to kick him out anymore. The story of Blood Brothers was based on a true story, an infamous murder case that took place in the early sixties.