10集全 9.0分播放：
Seasonfourofespionagedrama"MI-5"findstheteamreelingfromthelossofDanny(DavidOyelowo),butthrownbackintoactionwhenabombdetonatesnearhisfuneral.ZafarYounis(RazaJaffrey)andJulietShaw(AnnaChancellor)areintroducedtotheshow,inastoryinvolvingapotentiallydevastatingterroristattackinthecapital.LaterintheseasonLyndsayDuncangueststarsasaformerMI-5officerwithadeadlygrudge,onewhichthreatensthelivesofeveryonebackatTheGridaaa
