Three years ago travel writer Lydia Gard discovered freediving almost by accident. It's an extreme and beautiful sport defined by one simple objective: to dive as deep as you can on one single breath. Record holders are now routinely diving to more than 120 metres, pushing the sport and their bodies to find out what's humanly possible. Through her coach, Lydia was drawn into a small but fanatical community of competition athletes all united in their drive for depth, and that's where she stumbled on a darker side of the sport. Rumours swirled that a group of top divers were doping to get deeper, faster. As the community began to turn on each other over the allegations, one prominent diver decided to take the law into his own hands. A secret sting operation was meant to put an end to the problem by bringing the alleged dopers out of the dark, and into the light. But the issue hasn't gone away. And now, a lot of people who've been too scared to speak up, are ready to talk.

Journalist Rachel Sylvester investigates the case of 'Australia's worst serial killer'. And discovers, in a story about mothers who have been accused of murdering their own children, there is one man who connects them all: a doctor called Roy Meadow. Our thanks to The Francis Crick Institute for sharing recordings and insights.

Kathleen Folbigg is just trying to survive. She's a grieving mother, sentenced to life in jail for killing her four infant children. That is, until a small group of people start to question whether she might be the victim of a terrible miscarriage of justice. Our thanks to The Francis Crick Institute for sharing recordings and insights.

Kathleen Folbigg experienced unimaginable loss. All four of her infant children died suddenly, over a 10-year period. Their deaths were unexplained. Until a police detective turned up at her door, and arrested Kathleen on suspicion of murder. She was labelled ‘Australia's worst female serial killer', convicted, and was destined to spend most of the rest of her life in jail. Until a different type of detective entered her life. A scientist working in a lab who uncovered the truth behind the deaths. This is the story of a shocking miscarriage of justice, but as journalist Rachel Sylvester starts to investigate how this happened, she learns that Kathleen is not alone – other mothers have endured the same fate, and may also be in prison. The Lab Detective is a story about the power of science, and the determination of those searching for the truth.