Eddie Valiant (Mikka)
The younger of the two Valiant brothers, Eddie is the principal investigator of Valiant's Detective Agency. A calm, personable fellow with a knack for disguise.

Tommy Valiant (Jerry)
The older Valiant brother, Tommy was a pilot during the Great War and still commands a large measure of respect as a war hero. His recent exploits haven't been as exciting, though he does help with the cases at the agency from time to time.

Gerti Harper (Charles)
Gerti's the secretary for Valiant's Detective Agency, in charge of answering the phones, research in the libraries, and quite a bit of snooping herself. Gerti's been seeing Charlie Walker for a number of years, but no wedding seems imminent...

Charlie Walker (Nick)
Charlie's a dockworker on the Boston waterfront, who's helped the agency out when they've needed some extra muscle (or some company scouting around the seedier sections).

Peter Collins (Mike)
Peter is a freelance reporter, currently working principally for the Boston Globe. Peter carries the "investigative" in "investigative reporting" to great lengths in pursuit of a story - though he and his editors can differ on what is or is not publishable.

Dr. Juergen Schreber (Tom)
Dr. Schreber has consulted for the Valiants on esoteric medical evidence in some of their cases, though their acquaintance goes back farther, to when he was captured by Tommy Valiant as a prisoner of war in Egypt.

Roderick Bellesby (Andy)
At first appearances, Roderick appears to be a prosperous businessman. After a few minutes' conversation, however, he comes across as a bit of a nutcase with fixations on nutrition, the occult, and high fiber diets.

Esme Carrington-Danforth (Susie)
A dilettante and society girl, Esme is the niece of Miss Elena Saravelda and hires the Valiants to start the first run. However, rather than sit back and watch the investigators investigate, she seems interested in helping out...