The daughter of police officer Kostas Charitos has successfully completed her doctoral exams in law and is starting a vacation in Crete with her beloved. 

Just before the ship, carrying 300 passengers, enters Souda, it is seized by a group of masked men who give one-word commands in English. The police officer and Adriani rush to Crete, where police and military forces and relevant experts from abroad have gathered. 

However, Charitos' paternal anxiety gives way to duty, as the police officer must return to Athens to solve the most bizarre crimes. 

The killer is executing advertisement models, threatening to continue killing until the mass media, mainly television, stop broadcasting advertisements. The two seemingly unrelated cases, the piracy and the murders, after Charitos' persistent and subversive investigation process, prove to have the same origin.

The Principal Shareholder is one of the most powerful novels by the internationally multi-awarded Petros Markaris.