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Emmy nominee Elizabeth McGovern makes an assured return to Broadway as a lousy British mother in J.B. Priestley’s family drama “Time and the Conways.”

Toodleoo, “Downton Abbey.”

And while McGovern heads the Roundabout revival, the brightest star — if not the scene-stealing Dowager Duchess — is an eloquent and evocative set that underscores the themes of the 1937 drama about the fluidity of life and time. Sometimes you do walk out humming the scenery.

The action, set in Britain, begins in 1919 in the well-appointed Conway home. Self-dramatizing widowed Mrs. Conway (McGovern) and her six children, entertain. Post-war prosperity and optimism perfume the air as they play charades — an unsubtle clue that you can’t believe all you see. But acquaintances are made — fates are sealed.

The scene shifts to 1937. The set by Neil Patel recedes in full view as an identical room, but see-through, descends to take the original’s place. In effect, the past is visible through the present. Nearly everyone’s hopes have been dashed, one family member is dead. What went wrong? The last act returns to 1919, and even though there are frustratingly unanswered questions, we see how some seeds were sown for the future.

Without the time-leaping construction, the play is pretty conventional. It also has an annoying habit of overexplaining itself. In this case, a character quotes William Blake, noting that “joy and woe are woven fine.” Good and bad ebb and flow in life.

Well, yeah.

While ideas are underlined and highlighted, characters tend to be fairly one-dimensional. But under the sensitive direction of Rebecca Taichman (a Tony winner for “Indecent”), a first-rate ensemble breathes vibrant life into the adult Conway children.

That includes Anna Camp, as the born heartbreaker Hazel; Anna Baryshnikov as the youngest and sweetest Carol; Tony winner Gabriel Ebert as underachieving Alan; Brooke Bloom as rabble-rousing Madge; Matthew James Thomas as golden-boy Robin; and the always radiant Charlotte Parry as the thoughtful, would-be novelist Kay.

Steven Boyer, Alfredo Narciso and Cara Ricketts skillfully round out the cast as people who collide dramatically with the family.

“Time and the Conways” hasn’t been seen on Broadway, or in any major New York production, since 1938. It’s less known than Priestley’s “An Inspector Calls,” which concerns class, morality and family troubles. Come to think of it, its 1994 Broadway run, also featured an unforgettable set.

It was "Time" for another.