Now, we'll just watch this together, ma'am.
There it is now, there.
There he is.
He's by the sink.
And there he's washing.
There, right there, you see the flash?
Yes, Lieutenant, it's a cue blip.
And now the second one.
There.
There's the second cue.
Now that's the cue for the projectionist to make his changeover.
Am I right, Miss Freestone?
Yes, Lieutenant, I'm very impressed.
Excuse me, ma'am.
I don't mean to interrupt.
Right there, that high shot where the man's lying on the hotel bed.
That's where the new reel begins.
Just watch it, ma'am.
And there, that's where the man commits suicide.
And that's what the projectionist saw right after he got back from the shipping room.
That's what Mr. Mearhead told me.
He came back into the booth, looked up and he saw a man blowing his brains out.
You had to make the changeover right before Mr. Mearhead got back from the shipping room. Not a few minutes earlier, not sometime before, like he thought.
I'm afraid, in this case, Walter must be confused, Lieutenant.
He checked the footage counter before he left.
You must've fooled him about that, ma'am.
What I think, I think you changed the footage counter to place yourself in the projection booth at the time of the murder.
But really, ma'am, you had time enough to leave the booth and get to Mr. McAndrews' office.
Just enough time.
Because when you rushed back to make the changeover, that's when you must've dropped this glove by the projector.

Old timers used to unwind the reel and put a nickel in it near the end. The nickel would drop and wake them up if they fell asleep.