Matthew Island is a rock in the Pacific inhabited only by seabirds. Yet somehow it boasts a phantom ship registry. The roll offers cover for vessels that want to hide their identities. Members of the world’s growing “shadow fleet” use such tricks to smuggle sanctioned Russian oil and conduct espionage and sabotage—threats Western navies are struggling to contain.

And meet America’s newest moguls: the Ellisons. The family may soon control some of the country’s biggest news and entertainment brands—and have influence over the social-media app where American teenagers spend more time than anywhere else. How will they wield their new media empire?