Adelia (Vesuvia Adelia Rachel Ortese Aguilar of Salerno), a “doctor for the dead” working for King Henry II in 12th century England, by Ariana Franklin

Sister Agatha: former investigative journalist, now one of the extern sisters, the convent's link to the outside world, at the Our Lady of Hope Monastery, in New Mexico, by Aimée and David Thurlo

Albert Edward (Bertie), Prince of Wales, in England, by Peter Lovesey

Arcane Society: secret organization devoted to paranormal research, by Jayne Ann Krentz

Arcturus: the Roman governor’s doctor and investigator, in 83 AD Londinium, Britain, by Kelli Stanley

Aristotle, the philosopher, and Stephanos, a former student, in 330s BCE Athens under the rule of Alexander, by Margaret Doody

Dame Averilla: infirmaress at the Benedictine abbey near Shaftesbury in 12th century Norman England, by Barbara Reichmuth Geisler

The Bargain Hunters Network — Ginger the baby boomer, Kindra the college student, Suzanne the pregnant mother of three, and Mary Margret the silver-haired real-estate agent — in Three Horses, Montana, by Sharon Dunn

Dino (Delfina in disguise as a boy), an apprentice to Leonardo da Vinci, court engineer to the Duke of Milan in 1480s Milan, Italy, by Diane A.S. Stuckart

Elizabeth I: in 1500s England, by Karen Harper

Sister Fidelma: 7th century Celtic sister and legal advocate in Kildare, Ireland, by Peter Tremayne

Dame Frevisse: medieval nun in Oxfordshire, England, by Margaret Frazer

Abbess Helewise and Sir Josse d’Acquin, a French knight, at the Hawkenly Abbey in England during the 12th century, by Alys Clare

Hildegard: wealthy recent widow who becomes an abbess in late 14th century York, England, in the Abbess of Meaux mysteries by Cassandra Clark

Huy the Scribe, during the time of Akhenaten and Tutankhamun in the 18th Dynasty around 1350 BCE, in ancient Egypt, by Anton Gill

Iliona: high priestess blackmailed into spying for Sparta, in 5th century BCE Greece, by Marilyn Todd

Isaac: blind physician, and Bishop Berenguer, in 1350s Girona, Spain, by Caroline Roe

Sister Joan: investigative nun in Cornwall, England, by Veronica Black

John the Eunuch: Lord Chamberlain to the Emperor Justinian in Constantinople in 537, by Mary Reed and Eric Mayer

Miss Julia: elderly widow in Abbotsville, North Carolina, by Ann B. Ross

Kirsten: owner of the Wild Onion, Ltd, a private detective agency, and her husband Dugan, a lawyer, in Chicago, Illinois, by David J. Walker

Lassair: a 14-year-old girl with special gifts training to be a healer in a Fenland village, in 11th century England, by Alys Clare

Leonardo da Vinci: the James Bond of the Renaissance, by Robert Ross and Martin Woodhouse

Libertus: mosaicist and an expert in puzzles and patterns, living in the ancient Roman town of Glevum (now Gloucester), England, by Rosemary Rowe

Mac: ex-cop private investigator, in Chicago, Illinois, and later in Los Angeles, California, by Thomas B. Dewey

Mara: a female judge and lawgiver appointed by King Turlough Donn O’Brien in the early 16th century, on the west coast of Ireland, in the Burren mysteries by Cora Harrison

Sister Mary Helen: retired nun in San Francisco, California, by Carol Anne O'Marie

Mathilde of Westminster: physician and former lady-in-waiting, in the court of Edward II, in 14th century, London, England, by Paul Doherty

Merlin: scholar, doctor, and advisor to King Arthur of legendary medieval Britain, in the Merlin Investigations by J.M.C. Blair

The Nameless Detective, a private investigator in San Francisco, California by Bill Pronzini

Constable Nick: policeman in Aidensfield, North Yorkshire, England, by Nicholas Rhea (Peter Walker)

Nicolaos: investigator in classical Athens, beginning in 461 BCE, by Gary Corby

Preacher: poker player and mystic, in the American Southwest (Nevada, New Mexico, California), by Ted Thackrey, Jr.

Ramon, Lucio, Milos, and Neil meet for lunch and take turns to tell their stories, in the Lunch series by Derek Hansen

Odd Thomas: fry cook who can communicate with the dead, in the fictional small town of Pico Mundo, California, by Dean R. Koontz

Sister Ursula: a nun detective by H.H. Holmes (Anthony Boucher)

Victor the Assassin: the world’s deadliest hit man for hire, later working for the CIA, by Tom Wood

A police detective-sergeant in the Factory, Department A14 — Unexplained Deaths, in Soho, London, England, by Derek Raymond