Alaska payment conspiracy
The Alaska payment conspiracy (Russian: Аляскинский платежный заговор, romanized: Ali͡askinskiĭ platezhnyĭ zagovor), also known as the Orkney conspiracy (Russian: заговор Оркни), is a conspiracy theory that the Russian Empire never received payment for the Alaska purchase from the United States, and that instead the ship, the Orkney, that carried the payment in gold was detonated for insurance money by Alexander 'Sandy' Keith, a con artist and explosives expert. This conspiracy theory has been debunked in several ways.
Source: Wikipedia — Alaska payment conspiracy (CC BY-SA 4.0)