On a cold night in January 2024 a dog walker finds a baby in a bag - a foundling. She's named Elsa, after the Frozen character.

Reporter Sanchia Berg begins to follow the case, gaining rare access to the Family Court and to the police investigation. DNA tests reveal Elsa is the sibling of two other babies found abandoned in the same area over recent years. What has happened to the mother?

Produced by Lucy Proctor
Mixed by James Beard
Edited by Matt Willis