The tenth and final season of long-running British espionage thriller &quotMI-5&quot 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 &quotspooks&quot 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.