A 52-year-old cyclist has died after being knocked off her bike by a white van as she raced on a dual carriageway near Raglan in Monmouthshire. She was just nine minutes into a time trial with a group of other competitors when her ride was cut tragically short. With the van driver now under arrest and facing serious questions, Sergeant Cath Raine has been called in to investigate the final moments of the cyclist's journey. But the collision has happened on a concrete road, with barely a trace of evidence on its surface – and she knows that even a single mark could hold the key to justice. So when she finally discovers a clue at the edge of the carriageway, it raises more questions than answers.

PC Richie Wyatt is on a residential street in Risca, Caerphilly, after a powerful sports motorcycle collides with a brick wall. Two men were travelling on the bike at the time, and they have both been seriously injured. Close examination of the damage to the bike reveals the dynamics of the collision, but it's not proving straightforward to establish why the rider lost control.

In Chepstow, air ambulance doctors are treating a seriously injured woman after the car she was travelling in collided with a stationary lorry. She has been cut free from the wreckage, but as Sergeant Bob Witherall arrives at the scene, the damage quickly reveals the true extent of the impact.