As horrified as Sammy is by Terry's news that he's dead broke and has recently been in jail in Florida, his arrival is exactly the spark she needs to knock her life out of its deepening groove of order and rectitude. She's being tormented by a nit-picking boss (Matthew Broderick, wonderful in a small but crucial role) who has set himself a "personal challenge" to raise the standard of banking in Scottsville, and imprisoned by Bob's lukewarm affections.

A delicate-featured blond with something of Meryl Streep's regal bearing, Linney is an accomplished stage actress who has never quite gotten the right break in movies. She won't exactly knock your socks off here, but her performance as a woman who has almost accidentally developed a sudden savor for life is full of delicious moments. When Terry asks her if she wants to smoke some pot, she responds immediately, with a tone of offended certainty: "No, I don't." Then, a second later, she's his sister again: "Why, you got some?"

Terry, on the other hand, when asked to take care of his 9-year-old nephew, Rudy (Rory Culkin, the latest of his clan to break into movies), displays a surprising ease and maturity. Sammy rushes out of work one day when the baby sitter calls to say that Rudy hasn't turned up, only to find that Terry has brought him to a construction site and is teaching him how to hammer nails. He understands immediately that an uncle's role is to provide things a parent can't: post-curfew games of pool, frank late-night conversations. (Rudy: "Why are you smoking?" Terry: "Um, because it's bad. Don't ever do it.")

If there's a revelation in this cast, it's Ruffalo, who plays Terry as a peculiar mix of masculinity and vulnerability; his life is a mess, but at least he's not lying to himself about it. "I realize that I'm in no position to say anything ever," he tells Sammy during a quarrel, yet he seems mortally wounded when she wants to hire a plumber rather than allowing him to rip the house apart. Terry may be drifting through life, fatally unmoored, but he's the only person who suspects that Sammy is too, after her own fashion.

After Bob asks Sammy to marry him, she immediately embarks on a hilariously ill-advised affair with the stick-up-the-butt Broderick character, and at virtually the same time asks the preacher played by Lonergan to help convince Terry that life is important. (Talk about authorial intervention.) All of this plays out enjoyably enough; it's only when Terry and Rudy embark on a quest to find Rudy Sr., the kid's missing and mysterious father, that Lonergan seems to violate the terms of his own story. For the first time, "You Can Count on Me" seems like forced melodrama, in which some (relatively) cataclysmic event must occur to bring the story to a climax. Thankfully, it's a minor blemish on this fundamentally sympathetic minor-key fable of love and loss in America.

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