WHENEVER two siblings get together after many years – onstage, at least – you can expect dramatic revelations concerning secrets from the past.

Neil LaBute doesn’t mess with the formula in his latest effort, “In a Dark Dark House,” which opened last night.

The siblings in question are Drew (Ron Livingston), a well-heeled lawyer currently ensconced in court-ordered rehab (“It’s for us overzealous wine drinkers,” he jokes), and his older, blue-collar brother Terry (Frederick Weller), who’s come to visit.

The two men have the sort of alternately tense and jovial sibling relationship that results in a comic wrestling match within minutes.

But the reason for the meeting soon becomes clear: Drew wants his brother to testify about the childhood sexual abuse he suffered from a family friend, the better to garner sympathetic treatment for his adult addictions.

This being a play by the author of such tricky works as “The Shape of Things” and “Wrecks” (in which the payoff turned out to be incest), you can expect surprises, and they dutifully follow. The lengthy scene between Terry and a sexually precocious teenager (Louisa Krause) he meets at a miniature golf course has implications that aren’t revealed until later, and not everything about the two brothers’ past is as first presented.

But the play doesn’t quite crackle with the usual LaBute sizzle. The dialogue (and even the title) have an uncharacteristic generic quality, and the characters fail to engage our interest.

Long before the play’s secrets have been revealed, we have ceased to care, despite the fine efforts of the three performers. This work, like many others by this undeniably talented playwright, ultimately demonstrates a showoffy quality that seems more reflective of the head than the heart.

IN A DARK DARK HOUSE
Lucille Lortel Theatre, 121 Christopher St., at Hudson Street; (212) 279-4200. Through June 23.