Our Idiot Brother is a moderately funny offbeat comedy about a misfit with a heart of gold.

Ned (Paul Rudd) is a latter-day hippie type who lives happily on a run-down farm on Long Island, growing organic vegetables with his girlfriend Janet (Kathryn Hahn) and his dog Willie Nelson. Ned is not actually mentally deficient but he is basically incapable of lying or acting maliciously, or of believing that anyone else could do so.

While manning a stand at the local farmer’s market Ned is approached by a uniformed police officer who asks where he can buy marijuana. Ned naturally refuses to tell him, but when the cop says that he has had a bad week Ned relents and sells him a bag. Much to his astonishment he is promptly arrested and thrown in jail for eight months.

More disappointment awaits when he gets out. Janet has found a new, even dimmer hippie boyfriend (T. J. Miller.) She kicks Ned off the farm, but keeps his dog.

So it is up to Ned’s three sisters to try to help him get back on his feet. They are basically decent people but they have issues of their own.

Miranda (Elizabeth Banks) is a tightly-wound magazine writer. Natalie (Zooey Deschanel) is a somewhat inconstant lesbian. Liz (Emily Mortimer) is an ultra-pacifist married to a pretentious documentary filmmaker (Steve Coogan.)

They all love Ned but find him a trial to deal with. For one thing, you can’t tell him any sort of secret–he’s sure to blab it at just the wrong moment.

Nevertheless Ned fits closely enough to the “wise fool” archetype that things are bound to work out all right in the end. The moral, I guess, is that it is good to tell the truth but in any case you should do whatever is necessary to get your dog back.