I just went to take a picture of the detachable penis. Several factors motivated me. I’ll explain.

It’s well-known that Mark David Chapman carried a copy of The Catcher in the Rye on the night he murdered John Lennon. Richard Halpern, in his sharp new study, Norman Rockwell: The Underside of Innocence (University of Chicago Press), reminds us of another, even weirder pop culture connection—one that literally brought Chapman to New York and infamy. To pay for the death trip (and the fatal firearm), “Chapman sold his beloved lithograph of Norman Rockwell’s Triple Self-Portrait for $7,500.” “I find it suggestive that one icon of innocence was used to fund the assassination of another,” Halpern writes.

A passionate Rockwell fan, Halpern (a Shakespeare scholar by trade) suggests that “under the guise of innocence,” the paintings “often present potentially disturbing materials that they then dare the viewer to see and recognize.” In other words, sex is everywhere. The sanitized, sentimental scenes—a description critics and partisans can agree on—reveal darker material under this close reading. (Biographer Laura Claridge has noted that Rockwell, once a patient of Erik Erikson’s, “had always developed his narrative line through… an almost classical, psychoanalytically oriented process of free association.”) Rockwell’s Rosie the Riveter sports a strap-on. Christmas heralds sexual awakening. Dolls are disturbingly spread-eagled. In a dazzling deconstruction of 1955’s Art Critic (in which a snooty young painter stands before the portrait of an ample woman, peering at a piece of jewelry), Halpern not only highlights the real-life Oedipal tensions present (Rockwell’s wife Mary posed as the painted lady, and his son Jarvis, an aspiring artist, stood in as the museumgoer), but also compares the effete connoisseur’s hunched pose to that of Ingres’s famous Oedipus and the Sphinx.