You encourage the spread of these rumours of a Phantom.[…] But it seems not everyone is as afraid of ghosts as you hope. You're looking for jewels in an abandoned dressing room when an angry, hulking urchin walks in, swinging a cricket bat.
You whisper in a few ears, encouraging[…] urchins at the theatre to believe the rumours. Then all you have to do is rattle an old chain and the dressing rooms empty, leaving you strolling around picking up discarded jewels at your leisure.