[2] Hole learns that the ambassador had lost heavily in betting on Thai horse racing and had become indebted to notorious loan sharks.

Hole discovers that the Thai knife used in the killing had been treated with reindeer grease as used by the Sami people of Norway's far north, implicating members of Bangkok's Norwegian expatriate community.

He subsequently comes across Norwegian pedophiles taking advantage of Thailand's sex industry; ruthless entrepreneurs exploiting the city's gridlocked transport system; and scandals ensnaring Norway's ruling Christian Democratic Party and the recently installed Prime Minister.

Cockroaches also introduces the general atmosphere of intrigues and sinister power struggles in the higher echelons of the Norwegian government and Oslo police, which are a regular feature of the Harry Hole series.

[citation needed] It took a long time for the novel to be translated into English, with British and American publishers giving precedence to later books of the series, set in Harry Hole's home ground of Oslo.