The tenth and final season of long-running British espionage thriller "MI-5" sees Harry return to his post as head of Section D, wherein his Russian opposite Ilya Gavrik (Jonathan Hyde) proposes a strategic partnership between their countries. New "spooks" Erin Watts (Lara Pulver) and Calum Reed (Geoffrey Streatfield) join the fight to prevent all enemies of the alliance from sabotaging the plan and instigating a war.