Kidman, in a career-best performance, and Eckhart lend pitch-perfect calibration to the couple's shared and separate agonies. It's as if previous treatments of the subject were a series of failed experiments, and Rabbit Hole is the Eureka! moment.

Rabbit Hole is a tremendously sad movie, but it's also the furthest thing from a miserablist wallow.

It's an unforgettable, moving and brilliantly acted drama that richly deserves to be seen by anyone who cherishes great filmmaking.

Grief may be the topic under examination, but humor -- incisive, observant and warm -- is the tool with which it's dissected in Rabbit Hole, a refreshingly positive-minded take on cinema's ultimate downer: overcoming the death of a child.

Director John Cameron Mitchell - adapting David Lindsay-Abaire's play - has a surprisingly deft touch with this admittedly downbeat material; he builds dramatic intensity in subtle layers, rather than slapping it on with a trowel.