Right now, a digital wallet holds roughly 135 billion dollars. Anyone can see the balance, but nobody can touch it, and the owner vanished 15 years ago without spending a single coin. It is the greatest mystery of the digital age, and the suspects are a wild cast of cypherpunks, hoaxers, and accidental victims.

This episode pieces together the digital breadcrumbs left by Satoshi Nakamoto, the pseudonymous creator of Bitcoin. We explain the breakthrough that made the technology possible, trace the chronology of the disappearance, and weigh the candidates, before asking whether the identity even matters.

• Bitcoin solved the double-spend problem by making the network itself the ledger keeper, like an indestructible group chat of receipts that rejects any lie.
• Satoshi embedded a Times of London headline about bank bailouts int ...