Whatever reservations I have about The Mountaintop, Katori Hall’s lively, if dramatically questionable, take on the legacy of Martin Luther King, its value as an acting showcase cannot be overstated. Angela Bassett, now nearly two decades past her What’s Love Got to Do With It movie breakthrough (and looking not a day older), takes the stage with such vibrancy and playfulness, her work serves as a lesson on how to chew the scenery and make it seem like the most delicious meal in the world.

That’s no knock on her co-star, Samuel L. Jackson, who gets to play a humanized icon: Martin Luther King, Jr. on the night before his assassination in Memphis. The Mountaintop catches MLK in his hotel room, tired, missing his wife and kids, jonesing for cigarettes and coffee, and flirting with Camae, the hotel maid who brings them. As said menial, Bassett gets to balance girlish zest with a naughtier candidness. Within moments, this maid can flip from swearing to teasing to fawning as she decides how to treat this political superstar she finds equally desirable as a man and role model.

So far so good. As King and Camae trade cautious repartee, we enjoy the pleasures of an old-fashioned “will they or won’t they” build up, made extra interesting by the fact that the man happens to be a flawed, complicated, but undeniable, American hero.

Midway, playwright Hall throws in a potential wow of a twist: The maid might not be who she says she is. Could she be a spy for the FBI? A traitor from King’s own ranks? A woman from his past? Any of these avenues might have been better than Hall’s silly choice, which causes the second section of Mountaintop to decline precipitously. Once the maid explains her true purpose, all tension is lost. Instead of a romance or a political showdown, we get speeches, bargaining and platitudes. Hall is obviously just biding her time until the finale. That’s when Camae offers a quasi-poetic rap (accompanied by undeniably dazzling visuals) that treats King to a sped-up history lesson of his own legacy.

What could have been a grown-up look at the complexity of MLK’s character descends into a sophomoric mush of anachronisms and stalling. Nevertheless, a half hour watching Angela Bassett trying to save the evening beats a half hour spent doing most other activities, so it’s your call whether your trek to The Mountaintop is worth the slide downhill.