What if Nancy Drew ran a bookstore — and a mystery bookstore, to boot? This is the premise of “Mystery Woman: Mystery Weekend” (8 p.m., Hallmark), the first in a series of whodunit movies on the Hallmark Channel.

Kellie Martin, the spunky young star killed off from the cast of “ER,” brings her perky energy to this film as Samantha Kinsey, the owner of the Mystery Woman bookstore. Clarence Williams III (“Mod Squad”) plays Philby, her mysterious assistant. He may spend his days dusting off old first editions, but he has a background as a CIA agent. He’s also a past member of Yale’s shadowy Skull & Bones society.

If you believe that, you’ll have no problem with “Woman” and its rather farfetched plot about the mysterious murder of a mystery writer at Samantha’s mystery bookstore, or her incredible freelance efforts to solve the crime. The bookstore business must pay really well, because Samantha and Philby have all the time in the world to engage in evidence tampering, breaking and entering, and other illegal activities. I guess Philby must have worked for the agency before it was “reformed” way back in the 1970s.

Nina Siemaszko plays Cassie, Samantha’s best pal and the local district attorney, who thinks nothing of leaking information to Samantha. This irks Conners (Casey Sander), the no-nonsense and easily annoyed police chief who can’t seem to keep up with Samantha’s superior snooping, to no end.

For all of its preposterous excesses, “Woman” is a diverting, bloodless mystery of the old “Father Dowling” school, and as such is a welcome departure from television’s recent predilection for forensic morbidity.

Tonight’s other highlights

• Higher education on “Joan of Arcadia” (7 p.m., CBS).
• Martin Lawrence stars in the 2001 time-travel comedy “Black Knight” (7 p.m., Fox).
• Gregory Peck and Sophia Loren team up in the 1966 spy thriller “Arabesque” (7 p.m., Turner Classic Movies), directed by Stanley Donen.
• Sullivan’s case reaches its climax on “Third Watch” (8 p.m., NBC).
• A volleyball star contracts a mystery illness on “Medical Investigation” (9 p.m., NBC).
• Scheduled on “20/20” (9 p.m., ABC): makeovers and lifestyle changes for two overweight families.