Russian Roulette

An MI5 agent arrives in Aidensfield and shows more than just a passing interest in the activities of Vernon and his new business partner, a shady Russian businessman with a past grievance with the entrepreneur. Meanwhile, Tricia treats a manic depressive who deals with his demons by walking onto railway lines, whilst Mike decides to sit his sergeants exam when he comes across an old friend whose career has been a lot more ambitious than his.