‘St. Vincent’ is a movie that exists for one reason and one reason alone: to share the gift of Bill Murray with the world. Take Murray out of the equation and the flick is a maudlin mess. Include him and he at least makes the movie watchable.

Murray stars as the titular Vincent, a former Vietnam vet, casual alcoholic and lifelong curmudgeon. He lives in a house that’s falling apart, spends most of his day dodging bookies demanding money and the rest placing bets. When he’s not drinking or gambling, he also has a pregnant Russian stripper/prostitute (a bizarrely, yet brilliantly cast Naomi Watts) to kind of call a girlfriend, as well as an ex-wife with dementia he visits in a nursing home for all of the “aw shucks” moments that implies.

The plot kicks into gear when a sad single mom (Melissa McCarthy) and her hyper-smart, uber-cute and inexplicably unpopular son (Jaeden Lieberher) move in next door. One night, McCarthy asks Vincent to babysit her boy out of desperation. Vincent accepts because he’s even more desperate. The next thing you know, the kid and Vincent are spending all of their time together. From there, we’re in ‘Bad News Bears’ or ‘Bad Santa’ territory, in which a bad influence role model secretly ends up being the best thing that could ever happen to a troubled kid. Just in time for the third act, a number of troubling revelations make things all mushy and dramatic, but only to be turned around when the boy is assigned a project at Catholic school to find a contemporary saint. (See title for details.)

The film marks the first proper lead role that Bill Murray has accepted since ‘The Life Aquatic’ a full decade ago. In that time, he’s grown from a beloved comedy icon into a full-on legend. When he wasn’t stealing movies away in small parts, he compiled a surreal second life as an internet meme popping up tending bar in Austin, driving golf carts through Italy, randomly appearing at house parties, and just generally being his onscreen persona in real life. Finally agreeing to carry a movie again, Murray is indeed magnificent. Despite essentially playing a stock curmudgeon who learns to feel again through a precocious child, the actor delivers a genuine performance. He completely inhabits his assigned grump and manages to inject a little spontaneity and edge into even his most tiresome scenes.

It’s enough to have gotten a few folks giddy with Oscar rumors, but such things are out of place here. Is Murray great in the movie? Sure, but no more or less than he is in just about any movi. We just get more Murray than we’re used to these days. All his ticks and tricks are on display, with even the central Murray-as-mentor-for-troubled-kid angle coming straight out of the star’s old playbook in both ‘Meatballs’ and ‘Rushmore’. He might be the reason to see ‘St. Vincent’, but that’s not the same as saying that he’s stretched himself to deliver something special. This is Bill Murray being Bill Murray, and that just happens to be one of the great joys of American cinema.

Unfortunately, everything around Murray in ‘St. Vincent’ is a bit rough. First time writer/director Theodore Melfi’s script regularly teeters on the wrong side of melodrama. For the first hour, the balance of comedy and tear-jerking feels right. Then in the last half, Melfi whips out divorce, a death, a stroke, recovery, and in-fighting all at once. This type of comedy needs a dramatic gear shift in the third act, but Melfi crams in three simultaneously and almost kills off all the good will through sheer manipulative overload.

Things settle down enough towards the coda to keep disaster at bay, but there’s no denying that ‘St. Vincent’ is a pretty route tear-jerking comedy carried entirely on the back of Bill Murray and the built-in audience adoration that he brings. The other actors are fine, with Lieberher faring far better than the average child star. McCarthy does what she can with a stock Sad Mom role. Chris O’Dowd improvs a few extra laughs, but best of all is Watts turning a hooker with a heart of gold and a wacky accent into a weirdo scene stealer.

There’s enough talent and charm within the cast to smooth over the screenplay’s rough edges and make ‘St. Vincent’ perfectly pleasant escapism. Melfi sure is lucky to have landed Bill Murray, though. Sub any other actor into the role and the movie is instantly forgettable. Plug in that national treasure and he makes ‘St. Vincent’ feel special just long enough to stick in your memory for at least the ride home.