|Affiliations:||Central Intelligence Agency|
|Relatives:||Annie Walker (ex-girlfriend)|
Ben Mercer is a wanted person by the CIA. He and Annie Walker spent three weeks together in Sri Lanka, and fell deeply in love, but he left in the middle of the night, only leaving a note which read, "The truth is complicated, forgive me". At the end of the first episode, Ben shot a Russian assassin who was choking Annie, saving Annie's life. This was the real reason the CIA kept Annie around; they needed her to draw out Ben, hoping to catch him in an attempt to contact her.
He reappeared in the episode In the Light showing off impressive hand-to-hand combat and parkour skill as he tracked down an arms dealer named Hassan Waleed. He eventually found him at the same time as the CIA was attempting to arrest him, and killed him through a sniper rifle. As he made an impressive escape across several containers he came across Annie and seemed surprised to find her there, hinting that he may not know that she joined the CIA. Jai Wilcox noticed him behind them and chased after him alone, deliberately not alerting the others. After a short chase he drew a gun to force Jai to stand down and let him escape.
It is revealed that Ben is a former CIA operative and has gone rogue in order to take down terrorists. This is initially the reason why the CIA/DPD took Annie out of training early in the hopes of luring him out of hiding.
When Ben appeared to help Annie, he took a bullet for her.
It is revealed in the Season 2 premiere that Ben survived the gunshot. He was taken to a hospital where he noticed that the nurse disappeared. Annie was able to help him escape from an expert techy and was able to kill the two men. She escaped with him, he was transferred to another hospital where Jai gave him a hard time. He was taken out of the hospital by Arthur Cambell when he was ready before Annie checked up on him. He was swiftly put back into the field as a reinstated CIA agent.
After some time Arthur orders him to travel with Joan and Annie on a hostage scout mission when a group of people take 7 hostages including a CIA agent and good friend of Joan's. However, when the 3 of them become hostages themselves, he assists with the plan to escape and captures the two men responsible for this. The team succeeds in capturing the leader of the gang members and rescuing the hostages (including the CIA agent).