The architect Ludwig Mies van der Rohe was famous for the aphorism "Less is more." Though his design was guided by an abstract philosophy, his steel-and-glass buildings were outwardly simple and direct. 

There's something of Mies' maxim in Richard Greenberg's Pulitzer-nominated Three Days of Rain, directed by Tom Moorman in an uneven Defunkt production. Its structure is elegant and its language hyperarticulate, but behind its clean exterior there's a thorny emotional through-line. In the first act, set in Manhattan in 1995, impulsive Walker and his sister Nan reunite before the reading of their father's will. Their father was a lauded architect—on a level with Mies, whose Farnsworth House gets name-dropped in the play—but cold and taciturn with his children. While squatting in his father's old apartment, Walker has found his journal. It's filled with infuriatingly opaque entries, and Walker lassoes the unwilling, uptight Nan into joining his investigation of the past. Matthew Kern plays Walker as a volatile and flamboyant egoist, in love with his own words and unconcerned for his sister (Christy Bigelow). Then enters Pip (a dynamic Spencer Conway), the charming son of their father's long-dead partner, and tensions boil over as dangerous revelations come into focus.

In act two, Greenberg jumps 35 years back in time, and we meet the previous generation. Walker and Nan's father, Ned (Kern, affecting an unconvincing stammer), is a struggling architect while Pip's father, Theo (Conway), is just as ebullient as his son. Bigelow plays boozy Southern belle Lina, tartly described in the first act as "Zelda Fitzgerald's less stable sister," who comes between the two men. The parallel structure offers a fascinating prism through which to examine the legacies and secrets parents hand down, as well as the misinterpretations their children contrive. But the second act stumbles, and Bigelow in particular. Lina should possess both pluck and desperation, but Bigelow lacks spark, and there's no heat between her and Kern. Conway is largely absent in the second act, so rather than the love triangle coming to light, it just grows cold. After a vigorous first act, in which Moorman and his cast construct a sturdy and compelling edifice, the peek behind the façade proves unsatisfying.

SEE IT: Three Days of Rain is at the Back Door Theater, 4319 SE Hawthorne Blvd., 481-2960. 8 pm Thursdays-Sundays through March 23. $15-$25 Fridays and Saturdays, "pay what you can” Thursdays and Sundays.