“Moby Dick” is the great fictional portrait of madness, with Ahab’s megalomania driving him to destroy everything in his pursuit of the great white whale. Now a film can bring you a more visceral look at the same condition and save you a lot of time and all that learning about ropes and oil and stuff. The movie is a documentary called “Overnight” about a Boston lad named Troy Duffy who was tending bar in Hollywood when Miramax’s Harvey Weinstein bought a Tarantino-esque spec script Duffy wrote called “The Boondock Saints.” Duffy’s stunning overnight success is picked up by the media — Weinstein bought the bar he worked in and made him a partner, then agreed to let him direct the movie, AND Duffy’s band “The Brood” was signed to a record deal and to do the soundtrack for the film.

Duffy surrounds himself with friends, drinking pals, family and bandmates, including two who are making a documentary about him and his success as well as co-managing the band. Duffy is one of those rare guys whose ego is seemingly ginormous from birth. He is never shown for a moment doubting himself, only insisting that he and his friends are going to make film and music history, despite the fact that within six months Miramax scuttles the film, almost certainly because of Duffy’s obnoxious attitude. Gradually the movie does get made, but still everything turns to crap and the movie gets no distribution deal. Duffy gets his comeuppance, but never acknowledges a single aspect of it.

It’s a horrifying ride, really, watching this hateful guy, so clearly out of control from the outset, drinking and swearing (incessantly) as his friends look on, dopey-eyed and afraid to argue. When the film and record companies have turned on him, he lets loose a classic anti-Semitic blast. He’s garbage with legs, basically, and the movie lets you in on every gorgeous second of his demise.