Frank Wolff was a mathematical scholar who appears in Destination Moon and half of Explorers on the Moon. Herge described Wolff as clever, with an honorary master's degree in Mathematics with Mechanics, but also very feeble and quiet. Wolff is the rocket engineer who assists Tintin's friend Professor Calculus both before and during the Syldavian expedition to the moon.However, Wolff is eventually exposed as a spy who was coerced into helping an unnamed foreign power named Colonel Boris to hijack the moon rockets, blackmailing him by use of his large gambling debts. Later on, he helps the others confront Boris Jorgen, who had smuggled aboard the Moon Rocket, which results in the latter's demise. On the return trip, Wolff is guilt-ridden and sacrifices himself for the survival of the group by space exposure, ensuring the rest of the crew have enough oxygen to return to Earth with.