Edmond Hamilton’s 1942 Outlaws of the Moon is the tenth volume in the Captain Future series.
Curt “Captain Future” Newton, android Otho, robot Grag, and living-brain-in-a-box Simon “The Brain” Wright ventured into deepest space in quest of a secret that could save dying Mercury. For fear of raising false hopes, Newton kept the mission secret. Enough time has elapsed since anyone has seen Newton and his Futuremen1 that the Solar System has concluded that Newton and his chums must be dead.
On the plus side, this means that the secrets of Newton’s hidden lunar laboratory are open to anyone who can find it. Corrupt scientist Wissler is certain he knows how to do so. The Moon is notoriously deficient in useful minerals, including radium. All Wissler needs to do is look for concentrations of radium. Radium in sufficient amounts to show up on a detector must be Captain Future’s private radium stock.
Well, no. Wissler does find radium but not where he expects to find it. Captain Future, it seems, lied about the Moon’s mineral resources.