| sergeant(agent, informer, reporter, gumshoe) |
| shoofly(agent, informer, reporter, gumshoe) |
| slewfoot(agent, informer, reporter, gumshoe) |
| spook(noun, plant, agent, operative) |
| undercover agent(noun, expression, plant, watch, agent) |
| watch(noun, verb, examine, discover, scrutinize) |
| advance(watch, guard, lookout, patrol) |
| adventurer(watch, guard, lookout, patrol) |
| escort(watch, guard, lookout, patrol) |
| guard(watch, lookout, patrol, detective) |
| guide(watch, lookout) |
| investigating(watch, guard, lookout, patrol) |
| outpost(watch, guard, lookout, patrol) |
| outrider(watch, guard, lookout, patrol) |
| pathfinder(watch, lookout) |
| pioneer(watch, guard, lookout, patrol) |
| reconnoiterer(watch, guard, lookout, patrol) |
| recruiter(watch, guard, lookout, patrol) |
| runner(watch, guard, lookout, patrol) |
| vanguard(watch, guard, lookout, patrol) |