Adjutant-Detective Henk Grijpstra and Detective-Sergeant Rinus de Gier, along with their never-named elderly superior, the commissaris, are the most popular creations of Janwillem van de Wetering. They are police detectives in the Murder Brigade of the Amsterdam Municipal Police, and are featured in more than a dozen detective novels and several short stories published in Ellery Queen's Mystery Magazine and Alfred Hitchcock's Mystery Magazine.

Grijpstra, heavy, middle-aged, and less-than-happily married, is the senior partner of the team. He is a Frisian who in his youth dreamed of being a jazz musician; when a set of drums mysteriously appeared in police headquarters he appropriated them and refuses to return them.

De Gier, younger and almost effeminately attractive with deep brown eyes and curly hair, is single and very successful with women. A native of Rotterdam, he is also an amateur musician. He often carries a small flute, and in odd moments he and Grijpstra will improvise together in their office.

The commissaris, small, elderly, and often nearly incapacitated by joint pains, supervises the partners' field investigations. Intelligent and broadly experienced, he often provides key insights into his juniors' cases. A Frisian like Grijpstra, he is fond of jenever and small cigars; only his first name, Jan, is ever given.

Grijpstra, de Gier, and the commissaris first appeared in Outsider in Amsterdam (1975). Refer to Janwillem van de Wetering for a listing of the Grijpstra and de Gier novels.