What do you get when you mix stolen paintings, the Boston mob, a $5 million reward, Sen. Ted Kennedy, and an eye-patched, bowler-wearing 75-year-old detective with a prosthetic nose? Stolen, an inconclusive art-heist documentary that feels like an obscure PBS film a lazy substitute teacher would show in high school.

Stolen follows eccentric detective Harold Smith as he investigates the 1990 theft of 13 paintings estimated to be worth some $300 million from Boston’s Isabella Stewart Gardner Museum. Smith’s been fixated on the robbery since day one, but his investigation elicits nothing more than ridiculous voice-mail leads from all over the world. (Audio snippets of these messages become a unifying motif in the film.)

The most notable canvas among the missing bunch (which includes works by Rembrandt, Degas, and Manet) is Vemeer’s The Concert. Its theft seems both a violation to the museum and the legacy of its charismatic and celebrated founder (1840–1924). Besides Smith, there’s a quirky cult of obsessed Gardner-heist fanatics. We also hear from Tracy Chevalier (author of The Girl With a Pearl Earring) and a gallery attendant who fell freakishly in love with John Singer Sargent’s portrait of Gardner at age 13, and has worked at the gallery for 45 years. Unfortunately, director Rebecca Dreyfus doesn’t know what to do with this fantastic set of characters and old newsreels (including Gardner herself). The choppy, amateurish editing fails to weave her several plotlines into anything more than an unfinished patchwork of tangents and voice-overs.