Guest Stars Victoria Pugh as DSI Susan Lynn Sarah Tempest as Alys Mitchell Lisa Victoria as Catrin Pritchard Ffion Dafis as Kelly Owen Owain Gwynn as Sion Wells Bryn Fôn as Hefin Mathews Lois Elenid as Beca Mathews Jac Jones as Liam Pritchard Manon Prysor as Rhian Jenkins Gruffydd Wyn Jones as Jason Williams Sion Pritchard as James Rhys Mark Robert-Flanagan as Karl Lewis Paul Whitlock as Roy Carys Gwylim as Siwan Morgan Dafydd Wyn-Roberts as William Jenkins Sian Beca as Athrawes Gwyddoniaeth