In the once peaceful parks of Stockholm, a killer is stalking young girls and disposing their bodies. The city is on edge, and an undercurrent of fear has gripped its residents. Martin Beck, now a superintendent, has two possible witnesses: a silent, stone-cold mugger and a mute three year old boy. With the likelihood of another murder growing as each day passes, the police force work night and day. But their efforts have offered little insight into the methodology of the killer. Then a distant memory resurfaces in Beck's mind, and he may just have the break he needs.