Ellery Queen (1975)

S1E7 The Adventure of Colonel Niven's Memoirs

During a book tour in New York, Colonel Alec Nivin, a WWII spy, promotes his memoir that names several individuals involved in war crimes and treason. While staying at a hotel, Jenny O'Brien, Ellery's girlfriend, discovers Nivin's lifeless body, brutally stabbed with an old dagger. With the mystery surrounding his death, everyone except Jenny becomes a potential suspect in this unfolding drama.