WATCH THIS: MONDAY
“Magnum P.I.” (8 p.m., CBS): Magnum and Higgins (Jay Hernandez, Perdita Weeks) are understandably shaken when one of her former MI6 colleagues abruptly turns up nursing a fresh gunshot wound in the new episode “Day of the Viper.” They’re even more alarmed, however, by the news he has to deliver: The assassin who killed Higgins’ true love has resurfaced on Oahu. Ian Pryce guest stars.