Is Bernie Tiede (Jack Black), a funeral director and arts aficionado in small-town East Texas, merely a gentle fellow with a good heart, unable or willing to separate himself from a lonely older woman, the rich but arrogant and frequently mean-spirited Marjorie (Shirley MacLaine)? Or are his signs of affection, including a willingness to accompany her on international trips and, eventually, move in with her, merely prelude to a dastardly plot to put her on ice and benefit from a financial windfall?

“Bernie,” reuniting Black with his “School of Rock” director Richard Linklater, teases out the true-life mystery in a manner that more often than not is quite engaging; it’s a dark comedy with real kick, provided in part by “interviews” with the local townsfolk — played by area actors and nonprofessionals — in Carthage.

Black turns in one of the most affecting performances of his career, revealing the desperation and loneliness behind the happy-go-lucky facade. But MacLaine is first rate, too, handily demonstrating how and why Marjorie might have gravitated to Bernie. And Matthew McConaughey makes a strong impression in a small role, as a district attorney whose drawl and laidback mannerisms belie sharp instincts for sussing out the truth behind the woman’s disappearance. It’s all amusing and, eventually, a bit horrifying.