| In 1994, a toddler disappeared from a small Welsh village, never to be seen again. 23 years later, in London, the mother of rising cello star Matilda Gray commits suicide, without apparent reason. Among her possessions, Matilda discovers tantalising evidence, linking her mother to the Welsh girl's disappearance all those years ago. |
| Name | Character | Episodes |
|---|---|---|
| Tara Fitzgerald | Sylvia Walsh | 6 |
| Lydia Wilson | Matilda Gray | 6 |
| Richard Harrington | Aron Morgan | 6 |
| Clare Calbraith | PC Graves | 6 |
| Simon Kunz | Lloyd Satlow | 6 |
| Brendan Coyle | Stephen Kendrick | 6 |
| Joel Fry | Harlan "Hal" Fine | 6 |
| James Frecheville | Nick Dean | 6 |
| Claire Rushbrook | Rose Morgan | 6 |
| Joanna Scanlan | Janice Gray | 6 |
| Sam Hazeldine | Sean Howell | 6 |
| Sian Reese-Williams | Trudy Franken | 6 |
| Ifan Huw Dafydd | Harry Franken | 5 |
| Pippa Haywood | Dr. Verity Satlow | 5 |
| Darren Evans | Constable Shortly | 5 |
| Dyfan Dwyfor | Ed Fenton | 4 |
| Jane Thorne | Meredith Dean | 3 |
| Oliver Lansley | Carl | 3 |
| Anastasia Hille | Laura | 2 |
| Rupert Lazarus | Emile | 2 |
| Bella Ramsey | Young Matilda | 1 |
| Caroline Martin | Ms Clancy | 1 |
| Indra Ové | TV Host | 1 |
| Caroline Berry | Mrs Robson | 1 |
| Nicola Reynolds | Natalie Franken | 1 |
| Nick Hobbs | Ewan Dean | 1 |
| Paul Blackwell | Paramedic | 1 |
| Tibu Fortes | Casualty Nurse | 1 |