Even with stars like Frank Langella and Susan Sarandon, it's hard to read the premise of "Robot & Frank" without being skeptical. Half of the film's plot sounds like a modest indie heist film ... but with a robot. The other half seems like "Gran Torino"... but with the young Hmong teenager replaced with a robot.

It's clearly the robot that makes these plotlines sound ridiculous and hokey. They're not as nerd-kitschy as pirates, zombies and ninjas, but robots are just barely more respectable. Luckily, thanks to some charming performances and a surprisingly clever script, "Robot & Frank" ends up being much more than just a gimmick.

Langella stars Frank, a retired cat burglar living in quiet solitude in the near future (robots and video phones are a common part of society). His grown-up kids (James Marsden and Liv Tyler) are getting worried about Frank's mental health, which has been slowly deteriorating. He walks to a local soap shop expecting it to be an old restaurant from his past, and he often asks his son how things are going at Princeton despite the fact that he graduated years ago.

To help Frank, his son buys him a helper robot (voiced in a HAL 9000-esque drone by "Shattered Glass" star Peter Sarsgaard). The robot's goal is to help organize Frank's life, get him into a rhythm and live healthier. The two have a contemptuous relationship until Frank discovers the robot's capabilities for picking locks and breaking the law. They start with stealing a rare book for Frank's librarian crush (Sarandon) but then escalate to a far more daring heist of a rich techno-hipster's house that brings the attention of the local sheriff (Jeremy Sisto).

As strange as this is to say, there's a friendly human chemistry between Langella and the robot. In the beginning, the two have a funny back-and-forth antagonistic relationship. The robot wants Frank to eat better; Frank wants the robot, or "death machine" as he calls it, to disappear forever. Even as the two become better friends, however, the dialogue keeps giving the title characters clever and interesting banter.

It could have been a typical cranky old man routine, but the script – the feature debut from Christopher D. Ford – keeps the material fresh and the characters genuine. It also helps to have Langella, who brings lightness as well as emotional weight to the role. He's comfortable with the comedic conversations but really shines as the film puts the focus on his fading, inconsistent memory. Frank's monologue in the middle of the movie in which he talks about working with the robot and slowly moves toward talking about his son is a beautifully touching piece of writing and acting.

In fact, as "Robot & Frank" goes along, the central relationship is not only humorous but very moving. The two have interesting conversations throughout the film about the mind and the meaning of existence. However, as the sheriff tightens his investigation, the discussions become more intense as both Frank and the robot have to come to terms with the delicate state of their memories.

There's a twist near the end that I'm not quite sure works, but for the most part, Ford's script and director Jake Schreier handle the emotional material just as well as they handle their constantly laugh-inducing comedy. A few of the minor characters also feel a little out of place. Sisto's sheriff weirdly flip-flops between being Frank's admirer and Frank's prosecutor, and the dweeby young snob they're robbing is just a bit too snooty to be believed.

These characters only stick out, however, because everything else feels so natural. Even the hollow, clanging score strangely fits with the nearby future setting. The romance is sweet, the friendship is charmingly funny and the story is full of surprises. Perhaps the biggest surprise, though, is how improbably enjoyable "Robot & Frank" is.