The Case of the Missing Martian MacGuffin

Previously

…As they dug into their sundaes, a faint, otherworldly hum emanated from the Chronometer, which Mia had insisted on bringing for a "post-case debrief." A single, tiny spark of light flickered within its depths, and for a fleeting moment, Marcus swore he saw his vintage alien lunchbox collection, neatly arranged on a shelf in his mind's eye, shimmer with an unusual luminescence. But then, a dollop of whipped cream landed squarely on his nose, and the moment was gone, lost in the delicious, messy reality of their victory.