Bionic Woman & Merlin star Michelle Ryan plays the mysterious Lady Christina de Souza who joins the Doctor on a bus-trip which takes a very unexpected detour into danger. British comedy star Lee Evans also joins the cast playing a character called Malcolm whose life becomes connected to the Doctor's under extraordinary circumstances & Noma Dumezweni returns as Captain Erisa Magambo
- last seen helping Rose & Donna save the world in Turn Left. Written by Russell T Davies & Gareth Roberts.