The Rifleman (1958)

S1E15 The Pet

Ward Haskins shoots Joe Flecker, who possesses incriminating evidence that could potentially blackmail him. Haskins suspects that Lucas might have received the information, as he was the one who brought Flecker to the doctor before his demise. Troubled by Haskins' actions, Lucas searches through Flecker's belongings and discovers a wanted poster for Haskins hidden in the sole of Flecker's boot. Meanwhile, Doc Burrage is found drinking in despair, mourning the loss of three children to an anthrax outbreak for which he has a new serum, but no one will let him use it in time. Haskins then heads to the ranch, where he gets bitten by Flecker's horse, now believed to have anthrax. Mark overhears that anthrax is fatal and grows anxious since he too was bitten by the same horse.