The 39 Clues: Cahills vs. Vespers (Roland Smith) Books in Order

Roland Smith’s contribution to The 39 Clues universe comes in the Cahills vs. Vespers arc, where the globe-trotting Cahill family faces a new enemy. In the original series, siblings Amy and Dan Cahill crisscross the world collecting ingredients to a powerful serum and untangling their family’s secret history. By the time of Cahills vs. Vespers, they’re seasoned adventurers—but now they’re being blackmailed.

The shadowy group calling itself the Vespers kidnaps key members of the Cahill family and issues an ultimatum: steal a series of priceless objects or watch relatives die. Amy and Dan are forced into high-profile crimes while trying to leave clues for allies and stay ahead of law enforcement.

Smith’s novel Shatterproof is the fourth book in this sequence. It opens with Amy and Dan on Interpol’s most-wanted list and orders from Vesper One to steal the Golden Jubilee, one of the world’s largest diamonds, from a museum in Berlin. The heist is only the beginning; the job hides a deeper objective linked to an ancient document known as the Apology.

The story darts from European museums to dusty archives and on to Timbuktu, mixing puzzles, ciphers, and double-crosses. Side characters from earlier books—including other Cahill branches and Vesper operatives—continue their own plots, so Shatterproof is best read in series order rather than as a stand-alone.

If you’re following the entire Cahills vs. Vespers line, slot Shatterproof in after The Dead of Night. On this page you’ll find details focused on Smith’s volume, but it sits within a much larger, interconnected saga.