The title of Leslye Headland’s “Cult of Love” at the Helen Hayes demands attention. The Dahl family cult began in childhood: Diana (Shailene Woodley), Evie (Rebecca Henderson), Johnny (Christopher Sears), and Mark (Zachary Quinto) attended church faithfully with conservative Christian parents Ginny (Mare Cunningham) and Bill (David Rasche), vacationed annually at Big Meadows Lodge in Shenandoah National Park, never slept at friends’ houses—Ginny feared molestation—and were coached rigorously to sing “Oh Shenandoah” in tight four-part harmony.

Now in their thirties and forties, they gather on Christmas Eve at the Connecticut farmhouse, which the script describes as “literally stuffed to the brim with goodies, evergreens and cheer… an oppressive display of festivities and middle-class wealth that pushes the limits of taste.” Mark arrives with wife Rachel (Molly Bernard), Diana with Episcopal priest husband James (Christopher Lowell) and their baby, Evie with pregnant wife Pippa (Roberta Colindrez), and Johnny late with his sponsee Loren (Barbie Ferrara), 126 days sober.

The evening begins with “When Joseph Went to Bethlehem” and “Children Go Where I Send Thee”—the family singing in unison, duets, and solos while grabbing instruments scattered throughout the room as Bill pounds the piano. Musical harmony is what holds the Dahls together. On this night, it’s not enough.

Headland reveals a family that has fallen into delusional dysfunction and homophobia, driven partly by mental illness disregarded for years. Ginny’s love comes with conditions; Bill’s love has none. One without the other does not make true love, and no one can break free from the matrix. Diana hurls homophobic slurs at Evie and Pippa, attacks Loren’s lack of faith, claims Loren’s addiction stems from denying God’s existence. Diana loses herself completely, beating her baby bump in a prolonged breakdown. Ginny finally blurts: “Bill can’t remember anything. He has Alzheimer’s.”

Evie and Pippa leave for their hotel, promising not to return for the family photo. Rachel leaves with Loren. But Evie and Pippa do return for the photo, suggesting that cults professing nothing but love are difficult to escape. As lights fade, the question remains whether this tipping point will be enough, whether this will be the last Dahl Christmas Eve—the only hope for this damaged and damaging family.

Trip Cullman’s direction allows the superb ensemble to surgically peel back Headland’s carefully constructed layers of dysfunction.