The Virus: Part 1 (S06E01)

The team is sent undercover in Iran when they receive intelligence that suspected terrorist Mehan Asnik is plotting a bomb attack on London. Their aim is to blow up Asnik in Tehran, making it look like a terrorist attack, but just as the team are about to detonate the charge, a train packed with civilians pulls up yards from the target. With the operation at a critical stage, the team must make a split-second decision that could cost many innocent lives. (iTunes)