to investigate a crime; to scout; to reconnoiter; reconnaissance; detection; a scout

to detect; to investigate

to detect; to sense

surveillance aircraft; spy plane

a scout; spy

to investigate (as detective); to solve (crime); to uncover (a plot); to sniff out; to break in and analyze; detective work; to scout

to scout; to spy; to detect

to investigate (a crime) and prosecute

to eavesdrop; to tap (telephone conversations); to intercept and investigate

to track down; to investigate and arrest

to interrogate during investigation

detective; investigator; scout; spy

investigatory

detection unit

detector tube

detector