请为《军情五处 第三季》写一段简短且吸引人的故事梗概，包括主要角色及演员，要清晰、干脆，能够很好地说明电视剧的情节及背景，但是不要透露过多剧情内容，结尾应留有悬念。
The British espionage drama "MI-5", provides more shocking twists and turns in its third season. Tom Quinn (Matthew Macfayden) disappears following a shooting and new man Adam Carter (Rupert Penry-Jones) rises to the challenge in Section B. After recovering from his injury, Harry (Peter Firth) tasks Adam with proving Tom's innocence. Later in the season Danny (David Oyelowo) and Zoe (Keeley Hawes) are sent on a mission that has tragic consequences for one of them.