He asks his Mossad friend, Chaim, working undercover in NY, to help smuggle him into Lebanon since the CIA has confiscated Brady's passport in order to keep him out of trouble. This favor results in Brady unwittingly being used by rogue Mossad agents to undermine the shaky peace talks. The Israelis also believe the terrorists Brady seeks are the same people they want to punish for their horrific treatment of downed Israeli pilots. They code name given Brady's operation is "Shohet" which means ritual slaughterer in Hebrew.
Brady has multiple personal problems: terrible nightmares of the years in captivity, guilt over surviving since his superior died without revealing that Brady was also CIA and related impotency undermining his and his wife's efforts to have a child. He has never killed before and is afraid he may not be equal to the challenge, especially since any hesitation might cost his life. Politics in the CIA and Mossad work against him at every turn-at one point even the Israelis are trying to kill him. And if he is recaptured by Hezbollah, they will be happy to provide the torture he escaped the first time.
To succeed he needs the help of an Iranian, Fatemeh Khasravi, with whom he worked years ago in Lebanon, but he prefers not to rekindle passions that simmered before his capture.