Christopher Kaeys was a young marine engineer from Glasgow, Scotland, when he accepted a position as watchkeeper on Carnival’s Princess Cruise Lines. By summer 2013, Kaeys, 27, was nine months on the job. He worked on a 952-foot ship named Caribbean Princess. With a capacity of over 4,300 passengers, Caribbean Princess boasted one of the largest carrying capacities in the Princess fleet, complete with 900 balcony staterooms, a deck of mini-suites, and an outdoor movie theater.

While guests enjoyed an exciting atmosphere on the upper decks, Kaeys’s job kept him in the bowels of the vessel. He worked in the engine room, where the ship’s propulsion work—and a lot more, Kaeys found out—took place.

By August 2013, Kaeys had resigned from his job and set into motion a chain of events that changed the course of Carnival’s future.