The exclamation point is often the horror and mystery writer's greatest enemy.
99.9% of the time, it belongs in dialog and only in dialog. Whenever I encounter an exclamation point used outside of dialog, I am suddenly pulled from the spell of the story (assuming that it was cast in the first place) and made painfully aware of the writers intent. Its the writer telling me, the reader, that this! Is! Supposed! To! Be! Exciting! Or! Shocking! Or! Revelatory!
It automatically tells me that the writer doesnt trust my intelligence and instincts as a reader enough to let me figure out for myself that something is supposed to shock or stun or scare me.
Consider the following examples, all of them lifted from recent horror stories Ive read:
He realized that he hadnt locked the door behind him!
And now they were going to kill her!
They werent alone in the house!
You couldnt believe how loud your wife screamed when you opened your eyes!
He was lost!
You get the idea. To say its melodramatic would be to succumb to gross understatement. The use of the exclamation point outside of dialog is, to my mind, a lazy cop-out all too frequently embraced by horror/thriller writers (and weve all done it, myself included). Think Im overstating my point? Then try this simple exercise: Pick any of the above-quoted lines, and when you reach the exclamation point, imagine that it is the first four notes of the Dragnet theme. Go ahead, Ill wait.
They werent alone in the house-Dum-Da-Dum-Dum.
Makes its use seem absurd, doesnt it?