The Guns of Navarone1961

[as the team prepares to leave, Miller comes stomping in]

Corporal Miller:
Everybody stay exactly where you are! The party's over. Somebody stepped on the cake!

[opens his case]

Corporal Miller:
Exhibit A: a clockwork fuse. Elementary and archaic, but they work. Only this one doesn't work, you know why? The clock's okay, but the contact arm's been broken off. This clock could tick away until Christmas, and it wouldn't set off a firecracker!

[throws it in a corner]

Corporal Miller:
Exhibit B: Exhibit B is missing! All my slow-burning fuses are gone, disappeared, vanished! Exhibit C: my time pencils.

[holds one up]

Corporal Miller:
Seventy-five grains of fulminate of mercury in every one of them, enough to blow off my hand. And very unstable, very delicate.

[He smacks the one in his hand against the bundle of the rest, then violently crumples the whole mess together, and throws them in a corner]

Corporal Miller:
Which means there is a traitor in this room.