We meet him just after the death of his father and custodian, and early scenes show the highly regimented Adam, now alone, and going about his proscribed routine (same meals, same clothes, same bedtime, etc.)
Even those ignorant of the disease will find this a wrenching situation - we know his father is gone, and we don't know how well Adam (Hugh Dancy) will be able to function on his own.
Adam has a job - he's a brilliant engineer - but it's tenuous, and his inability to connect with others leaves him vulnerable to the slightest setback.
Enter Beth (Rose Byrne), a new neighbor with a big heart who sees how lost Adam is and begins to help him out. Adam interprets these gestures as affection and develops a crush.
Beth is initially squeamish - he doesn't seem to be ideal "boyfriend material" - but the better she gets to know him, the more she likes him.
He's hardwired to be guileless. Part of Asperger's means that he cannot understand when another person is being ironic - when what they say is the opposite of what they mean. Many jokes are beyond him, especially the snide and the sarcastic.
Beth, who has just broken up with a deceitful, snide, sarcastic guy, is understandably pleased to meet a man who is none of those things.
The movie makes something of a strange romantic comedy out of their relationship that works well enough. Other elements do not - writer-director Max Mayer also wants to contrast the relatively innocent Adam with Beth's wheeler-dealer dad (Peter Gallagher), a subplot that lengthens "Adam" without deepening it very much.
It's the kind of movie that lives or dies by its leads, and "Adam" benefits from Dancy's tricky work conveying Adam's specialized intelligence, and the warm, generous contribution of Byrne, just nominated for an Emmy for her work on FX's "Damages."