In one of the most chilling terrorist attacks since 9/11, ten men armed with guns and grenades led a precisely-planned attack on Mumbai, India, in November 2008, leaving 168 dead.

Security forces took three days to end the violence, killing all but one of the attackers. The killers were soon identified as members of Lashkar-e-Taiba, a Pakistani militant group, but it later emerged that an agent had been in the city planning the attack for two years. He had passed unnoticed, as he was half-Pakistani, and he had the ideal cover -- he was an American citizen. Born Daood Sayed Gilani in Washington DC, he changed his name to David Headley (his mother's maiden name) to make travel easier. A convicted heroin smuggler, he had agreed to act as an informer for the Drug Enforcement Agency. But while visiting Pakistan to spy for the DEA he instead attended terrorist training camps. After the Mumbai attacks, he also flew to Britain to plot an attack on a Danish newspaper. He was arrested in 2009 en route to Pakistan.