The phrase "cloak and dagger man" refers to an individual who tends to operate in secrecy, often engaging in covert and mysterious activities. There are several synonyms for this term, including spy, secret agent, undercover operative, sleuth, and intelligence officer. Each of these words emphasizes the element of secrecy and deception associated with this type of work. Other related terms include infiltrator, mole, and double agent, which imply a willingness to infiltrate the ranks of an enemy organization in order to obtain secret information. These words all suggest a shadowy and dangerous world of espionage and intrigue.