When a delusional shut-in discovers that his favorite webcam model has been kidnapped, he must utilize his detective skills to locate her before she becomes another victim of a rampant madman.

I liked the detective skills part myself, it leads one to wonder if the shut-in might actually leave his house to do the investigation.

Somebody beat you to it.
http://www.imdb.com/title/tt2503154/

I would avoid to use favorite porn webcam model in the logline.
That make the protagonist seedy and creepy.
A reluctant h?ro is common, but a main character who the spectator does not respect is a big NO, NO.

Kidnapped by a gang of sex traffickers, a lonely neurotic nerd must save his favorite web-cam girl from them.

Anti-hero?

"When a deluded shut-in's favourite wedcam model is kidnapped, he takes it upon himself to rescue her from ... "

How does he know it's a rampant madman who has her? Or is he just guessing?

"... a notorious serial killer."

The stakes are a LITTLE unclear - I went with a notorious killer, because he could have heard this on the news, and then the implication is that her life is on the line - but I presume he equates his infatuation with her as love, and that if he rescues her she'll be smitten with him as well?

I think the idea has legs, just want this logline to be more streamlined, and possibly to have those questions clearer in the logline.

I knew I had seen a similar logline somewhere.
Amazon Studio had a competition on scripts and the winner had a script based on the very same premises.
It is called: I think that Facebook friend is dead.
It is supposed to be in rewrite before shooting.
Here is the link:
http://studios.amazon.com/projects/5046

http://ncis.wikia.com/wiki/NCIS_(series)

Again...thanks for all the feedback everyone.

Actually, that's one of the scenes in my script. Him trying to convince the cops was one of my favorite scenes to write.

OOOHHHH, that feels so much better.

Unfortunately, I don't watch NCIS, so you'll have to fill me in.

I would suggest something along the line.
I think that there was a CSI:New-York based on the same concept.
I would suggest something like:
After witnessing live on webcam the kidnapping of his only friend, a socially awkward genius must overcome his agoraphobia and use his investigative skills to save her from human traffickers.