Unseen Character Dialogue

[GreyKnight]

If I introduce a new character who is off-screen and has not been introduced yet. But he is in dialogue with a character on-screen, can I put his name in the dialogue, or must I leave it till I introduce him?

e.g.

JOE
Who's there?

JIM (O.S)
It's me.

or is this correct...

JOE
Who's there?

VOICE (O.S)
It's me.

[dpaterso]

I'd name the character, unless it's a mystery and you don't want the reader to know who it is until the proper moment of "TA-DAH!" revelation arrives.

-Derek
-----------------------"What? Am I the only sane one here? Why don't we drop the defensive shields?"
"A superlative suggestion sir, with just two minor flaws. One, we don't have any defensive shields, and two, we don't have any defensive shields. Now I realize that technically speaking that's only one flaw, but it's such a big one I thought it was worth mentioning twice."
(a few moments later...)
"I say let's break out the laser cannon and give 'em both barrels!"
"An adroit suggestion sir, with only two minor flaws..." ~Cat & Kryten, RED DWARF

[Deus Ex Machine]

I agree. Unless the mystery of the identity is important to the story then I would Identify the character. If the identity is intended to be a secret, as with Scream, I'd use MAN'S VOICE.