Thrillers like The Da Vinci Code provide an initial buzz, but as plot twists mechanistically pile up, puzzle solving becomes a chore. Sad to report, the great Jasper Johns’s work has devolved into similarly schematic riddles. In his latest show, the inscription “JSATSUPDEYRFJOORHMNESR0C2E” is stenciled across the bottom of Study for Merce (2002) in alternating red, yellow, and blue. (A hint for the cryptographically challenged: Use every other letter and be amazed. Or not.) But who would care if only the image—those same primaries painted in flat rectangles that extend onto slats hinged to the canvas— excited our cones and rods? For that you must go to the Met and ogle Johns’s masterpiece White Flag, an encaustic tundra masquerading as 48 stars and stripes as leached of passion as the Eisenhower era. Just as that complacent decade was actually a crucible of coming upheaval, the roiling drama of Johns’s frozen brushstrokes and collaged newsprint belie monochrome conformity. Now half a century old, the painting remains perpetually startling.

Sometime in the late ’60s—the period when he began deploying variations on Leonardo’s enigmatic “Mona Lisa”—Johns traded in sublime visual koans for mystery motifs, like the current rectangular shapes cribbed from the remnants of a large Manet canvas famously cut into pieces and later rescued by Degas. Executed in variegated grays, they cast an unintended pall over the exhibit. In a series of altered intaglio prints, paintbrush-wielding stick figures (refugees from a game of Hangman?) stand on a catenary—the curve formed by a cord hanging between two fixed points. These arcs are sometimes painted as shadows under actual strings hung from the slats. There are variations on these professionally wrought tricks, but like a paperback mystery left in an airplane seat pocket, their solutions are tedious and quickly forgotten.