After murdering a woman in a London park, the culprit left behind a witness: her two-year-old son. Can the little boy help police catch his mother’s killer before he strikes again?

In 1992, Rachel Nickell was brutally murdered in broad daylight in a London park. But her killer left behind a witness: her two-year-old son Alex. With the uneasy consent of his protective father, André, police spent months working with the toddler to coax details about the attacker. After André put an end to his son’s distressing questioning, police laid a honeytrap for a nearby suspect with violent sexual fantasies. They arrested Colin Stagg even though there was nothing connecting him to Rachel’s death. And when a similar murder stunned the city, investigators were at odds with one another on whether they had the right man.

The Netflix documentary “The Murder of Rachel Nickell” tells the inside story of the search for a serial killer. It features in-depth interviews with André and Alex about the toll it took on the two-year-old boy repeatedly asked to identify his mother’s murderer. It also explores how missteps by the police — before and after the crime — resulted in years of delayed justice.

OUR SPOILER-FREE REVIEWS OF "THE MURDER OF RACHEL NICKELL" BEGIN IN THE FINAL 10 MINUTES OF THE EPISODE.