I’ve long subscribed to the theory that no theatrical production is ever so blithering, soulless, or inept that it can’t offer patrons a few interesting discoveries. Scratch an Andrew Lloyd Webber musical and it’ll bleed enough Puccini to be instructive to the musically trained ear. Adrian Hall’s laughless The Taming of the Shrew provided Shakespeare Theater regulars with an object lesson in how a determined director can overwhelm comedy with concept. And Theater works’ purposefully amateur Romeo and Juliet—produced to give a hundred-or-so street kids from Pasadena and D.C. something to do this summer—offered audiences weaned on two- and three-character plays a rare glimpse of the raw power in a tumultuous onstage crowd. Those who watch carefully can glean staging lessons or acting tricks from the most lackluster revues and boulevard comedies.

But whatever Nancy Nilsson’s one-woman d(io)rama, Very Truly Yours, Mary Lincoln, has to offer in the way of theatrical edification, it offers only in the breach. Limply conceived and without discernible insight, the show isn’t excruciating; it’s just not worth attending for 85 minutes at Washington Shakespeare Company’s Clark Street Playhouse. Nor worth thinking about afterward. Count this as an accomplishment of sorts, since Mary Todd Lincoln is among the nation’s more troubled first ladies, one whose story practically begs for theatrical exploitation. Falsely accused of disloyalty during her White House years because of her Southern upbringing, she outlived her assassinated husband by almost two decades, sinking slowly into a desperation that was eventually judged to be madness.

When Nancy Grosshans’ Mary comes bustling on at the beginning of the show burbling that she has nothing to wear to Ford’s Theater that evening, the author seems to have hit upon a reasonable device for illuminating this soon-to-be-devastated character. You can almost map out the way events will unfold: Act 1 will concentrate on courtship, marriage, politics, and wartime stress, all leading to a haunting fade at intermission as Mary beams happily in the dress she will wear to Our American Cousin; Act 2 will present the harrowing tale of her mounting depression and descent into irrationality, which caused her 1875 commitment to the private sanitarium where she spent the last seven years of her life.

Alas, Very Truly Yours, Mary Lincoln isn’t nearly as sophisticated as that hypothetical synopsis, which assumes an elemental sense of drama Nilsson shows no sign of possessing. The author still has Mary in a dressing gown at intermission, doesn’t send her to Our American Cousin until the final curtain, and barely hints at mental instability to come. Working mostly from her subject’s letters (hence the title), Nilsson doesn’t depict her heroine as the more troubled partner in what must have been a complicated marriage (Abe suffered fits of despair that would have labeled him manic-depressive in this century). Instead, Nilsson’s Mary Lincoln is a chatty flibbertigibbet whose favorite topics are fashion (“gloves are elegant, don’tcha think?”) and her own flirtations. So little else is discussed during some passages that it almost seems Amanda Wingfield has wandered onto the premises.

Not everything is idle small talk. Occasional references to “that Tennessee ruffian” and “the butcher” (Andrew Jackson and Ulysses S. Grant, respectively) indicate that Mary was at least paying attention as her husband struggled to preserve the Union. And her commentary on the birth of the Republican Party might elevate her conversation if it weren’t paired with clearly delusional estimates of her own political acuity (“I am the abolitionist in this house”). Every time you’re tempted to take her seriously, she starts babbling about a new dress or sighing with a sweet petulance (“Oh, that war again…”) that makes her sound as if she has bubbles where her brain should be.

Grosshans makes the mistake of playing this over-amiable creature amiably, leaving the evening with no edge whatever. And her husband Robert Grosshans’ staging, which mostly has Mary darting from chair to chifforobe and back again, offers little in the way of period ambience or visual cleverness to help her make an impression. At one point, when the actress’s profile was centered, cameolike, in an oval mirror, I briefly thought I’d figured out why she kept drifting to the rear of the columned setting, but since the reflection could only have been visible from a few seats in the audience, it was probably happenstance rather than a calculated effect.