Captain Joe Martin arrives in Aden with his wife Honor to replace the outgoing and much loved Captain Nick Page of the Royal Military Police.

Led by Major Harry Markham, the Royal Military Police assist Special Forces on a dangerous mission.  Mary Markham experiences complications with her birth and Alison Laithwaite introduces Honor to the BP Club.

Captain Joe Martin meets with American journalist Martha Franklin to demand she hand over incriminating evidence. Christmas celebrations at the Royal Military Police base are cut short by a shocking discovery.

The RMP search desperately for George as the Markhams struggle to cope with his loss. Tilbrook brings Markham to see Abdul-Kadir Hakim in prison about George's kidnap. Alison attempts a self-administered termination but can't go through with it. Alison and Honor drive to the desert, their car breaks down and Honor guesses the truth about Alison's affair. Ed has a chance to rescue George but is attacked.

The NLF demand a swap, their leader Hakim in return for George Markham. Alison watches over Ed in hospital. Honor confronts Martha about her relationship with Joe. Yusra gets a coded message to Armstrong of their whereabouts. With Armstrong's help, Joe disobeys his orders to transfer Hakim and attempts to enact the trade instead, to rescue George and Yusra.

Joe faces court martial for disobeying orders, Ed offers to represent him. Fearing for Yusra's safety from the NLF, Armstrong leaves base to find her. Doctor Russell refuses Alison an abortion. In court Honor is devastated by Joe's secret past. Martha discovers a shocking truth about secret British Government negotiations. Markham breaks the rules and gives Ed evidence for Joe's case. Martha and Honor's discoveries lead to Joe's freedom.