• to nose after, to nose for
• to hound a dog on sy, to hound a god at sy
• detective, investigative, investigator, investigatory, plain-clothes man, plainclothes man, tail, tracer
• detection, enquiry, hunting, inquest, inquiry, investigation, quest, search
• department of investigation, investigation department
• to detect, to retrace, to scent, to trace, to track
• plain-clothes detective, plain-clothes policeman
• coroner's quest, crowner's quest