From the EON homepage:
The genesis for Henry Slesar's Edge of Night novel The Seventh Mask actually occurred before Slesar ever became a soap writer. In the mid-1960's with daytime dramas at the height of their popularity, serial producer Procter and Gamble decided to offer tv tie-in novels as a premium for P&G consumers. The company hired prolific mystery writer Henry Slesar to devise a mystery novel utilizing Edge of Night characters. While the actual mystery involved completely original characters who never appeared on the show, several familiar names were present as peripheral characters: Mike and Nancy Karr, Phil and Louise Capice, Bill and Martha Marceau, Winston Grimsley, Laurie Ann Karr, Ken Emerson, and Jeanne Culpepper. After Slesar completed the novel as requested, P&G opted not to publish as sales for other P&G premiums ("As the World Turns" and "Search for Tomorrow") had not performed as well as expected. Not long after, Slesar mentioned The Seventh Mask to his publisher at Ace. Ace liked the idea and decided to publish the novel in 1969. Ironically, P&G suddenly became interested in the project again and demanded that Slesar return the option he'd been paid for writing the book. The Seventh Mask was planned to be the first in a series of Edge novels (ala the Dark Shadows series published by Paperback Library); however, due to negotiation problems between copyright owner P&G and publisher Ace, further novelizations never reached fruition.
Although The Seventh Mask's narrative is rooted in events outside of The Edge Night's established storyline, the story and situations could have just as easily been a plotline from the show. In fact, the novel is classic Slesar: a "Daddy's girl" protagonist, a delightfully eccentric villain, abundant blue herrings, and of course, a Slesarian denouement.
The Seventh Mask opens with wealthy, young socialite Adrienne Haven returning home from a party at Phil and Louise Capice's Orchard Hill home. Adrienne discovers the body of her older husband Walter, shot through the head in an apparent suicide. Fearing that she'll lose Walter's insurance money, Adrienne quickly burns the suicide note and arranges the death-scene to resemble a botched robbery attempt. Naturally, Adrienne's plan backfires. The police are immediately suspicious, and when a nosy insurance investigator arrives in Monticello, Adrienne's volatile lover Tony Jerrick is arrested on a charge of first-degree murder. Horrified, Adrienne confesses the truth about Walter's death only to find that no one believes her. At Louise's urging, Adrienne turns to attorney Mike Karr for help. As Mike investigates the crime, he learns that there's a great deal more to Walter's death than meets the eye, including idiosyncratic blackmailer Joachim Fry who holds a secret that threatens the Haven family.
Despite such an unusual history, The Seventh Mask actually had a relatively long life. Six years after publication, a teleplay based on the novel appeared on ABC-TV. At the time, Henry Slesar was a consultant for the ABC Wide World Mystery, a late-night series of filmed and taped 90 minute mysteries. Slesar was assigned to work with two other writers, who had an idea for a story that was similar in nature to The Seventh Mask. Remembering the already written novel, Slesar and his associates simply changed the names of a few characters and adapted The Seventh Mask into a 90 minute teleplay entitled "Please Call It Murder". Ironically, The Edge of Night itself nearly became a permanent feature of the ABC Wide World Mystery eleven months later when Edge moved from CBS to ABC.
ABC WIDE WORLD MYSTERY
"Please Call It Murder"
Airdate: Tuesday, January 21, 1975. 11:30pm - 1am ( Eastern Time).
Format: 90 minutes. Color. Videotape.
CAST:
Lt. Danny Ianello... BRADFORD DILLMAN
Joan Harper... KATHLEEN WIDDOES
Susan Browning... JANET MARGOLIN
Dr. Vincent... HENRY JONES
Mickey Costigan... SIMON OAKLAND
Sawyer... LOU TRIANO
Joachim Fry... DEAN SANTORO
Woodward... ERIC BROTHERSON