"Never back down" means:
He saw his target—a man in a gray suit, unremarkable in every way except for the silver briefcase handcuffed to his wrist. The man stepped onto the magnetic rail platform just as the doors began to hiss shut. secret+mission+undercover+agents+never+back+down+link
So, what drives undercover agents to take on such high-risk missions? For many, it's a sense of duty and a desire to serve their country. Others are motivated by a sense of adventure and a need to push themselves to the limit. "Never back down" means: He saw his target—a