IN THE FRAME, by Dick Francis (Harper & Row, $8.95). The ex-jockey turned author has come up with another winner. No matter that the horses are painted subjects on canvas as Francis turns from the stables to the painter's studio in this tale of an art-and-antique gang thieving around the world. It still is a thoroughbred thriller in the Franciscan style - fast pace, lean prose, tough and laconic hero.

LAST DITCH, by Ngaio Marsh (Little Brown, $7.95). In a collaboration that started back in 1934, Dame Ngaio and Scotland Yard Superintendent Roderick Alleyn return for another delightful adventure in detection. A young woman is killed when her horse fails to jump a ditch, and Alleyn's son, Ricky, now grown to college age, finds himself among scruffy painters, religious fanatics, and drug smugglers. This is for those who don't require headlong action and savor Dame Ngaio's sharp perceptions and impeccable style.

THE PEKING MAN IS MISSING, by Claire Taschdjian (Harper & Row, $10). This is one of the most off-beat and original mysteries of the year despite story-telling shortcomings. Taschdjian, who herself was a laboratory assistant in Peking and helped pack the fossils on the eve of the Japanese invasion, reconstructions what might have happened to the still-missing bones - an unsolved archeological mystery to this day.

LAIDLAW, by William McIlvanney (Pantheon, $7.95). This promising mystery debut by a Scottish poet-novelist introduces Jack Laidlaw, a Glasgow detective - dour, introspective and abrasive. Like the Wahloos with their Swedish series featuring Martin Beck, McIlvanney transforms the police procedural into a vehicle for human and social observation. He is an exciting new talent.

THE SUNDAY HANGMAN, by James McClure (Harper & Row, $8.95). Against a contemporary background of racial unrest in South Africa, this newest McClure mystern unfolds with the team of Afrikaner Lt. Tromp Kramer and his Bantu sergeant, Zondi. The murder mystery - a hanging that turns out to be an execution instead of an apparent suicide - is the tale on which McClure hangs a searing indictment of South African apartheid society to the detriment of blacks and whites alike.

DETECTIONARY, edited by Otto Penzler, Chris Steinbrunner, and Marvin Lachman (Overlook Press, $15). This biographical dictionary will be a trusted and helpful companion for whodunnit readers. It lists sleuths in mystery fiction from the time Edgar Allan Poe introduced M. Dupin, the first detective, up to the square-jawed Dick Tracy. There are also sections on rogues and helpers, cases, and crime films with a splattering of illustrations. The entries go beyond names to idiosyncracies, methods of detection, and evaluation of place in the mystery canon.

DEATH OF AN EXPERT WITNESS, by P. D. James (Scribner's $8.95). The murder of a scientist in a forensic laboratory laboratory allows this perceptive novelist to explore human relationships through Adam Dalgliesh, the professional policeman who is also a poet and a man who thinks and feels. James writes substantial novels, which also happen to be mysteries, for readers who want more than a diverting escape.

THE SECOND DEADLY SIN, by Lawrence Sanders (Putnam, $9.95). This sprawling bestseller treats greed and avarice against the backdrop of the New York art scene, drugs, models and mistresses; a love-hate relationship between father and son, jealous artists, a fatal illness, and a mysteriously locked barn.

ALFRED HITCHCOCK PRESENTS: STORIES THAT GO BUMP IN THE NIGHT (Random House, $8.95). The mystery short story is a difficult and demanding form for writers, and most collections tend to be erratic and uneven. The Hitchcock volume, with his special touch for the macabre, has entries by Ambrose Bierce, Roald Dahl, and Patricia Highsmith.

MURDER INK: THE MYSTERY READER'S COMPANION, compiled by Dilys Winn (Workman, $14.95 cloth; $7.95 paper). This is the Whole Earth Catalogue of crime fiction as perpetrated by Dilys (as in "kill us") Winn, the founder of Murder Ink, the first bookstore devoted exclusively to mystern fiction. It is an irreverent compendium from some 150 contributors with such relevant and irrelevant information as: the number of Hercule Poirot's "little grey cells" (approximately a trillion, or 10 to the twelfth power); the most famous fictional blunt instrument (Roald Dahl's frozen leg of lamb); a poisoner's pharmacopoeia; the history of the trench coat; and a timely list of Christmas-time fictional murders.

There are also three other collections that make good bedside companions for those not bothered by nightmares: WHEN LAST SEEN, edited by Arthur Maling (Harper & Row, $10.95), the annual anthology of the Mystery Writers of America with this year's theme of mysterious disappearances; BEST DETECTIVE STORIES OF THE YEAR, edited by Edward D. Hoch (Dutton, $8.95), with a Ruth Rendell gem of suspense; and ELLERY QUEEN'S SEARCHES AND SEIZURES (Dial Press, $8.95), a collection from the monthly mystery magazine of the same name.