Murdoch investigates the apparent murder of a young woman whose death was clearly made to look like a suicide. From the young woman's calloused index finger, Murdoch knows that victim was a telegraph operator. He knows this as his new friend Enid is also a one-time telegrapher and she works closely with Murdoch, much to Dr. Ogden's dismay. They soon learn that the dead woman may have been carrying on, at least over the telegraph wires, with another telegrapher with the initials AK. They set up a trap for him but Enid takes offense when Murdoch uses her own information to set a trap. Another body narrows the field of possible suspects but it becomes apparent that the mystery man knows who Enid is. Inspector Brackenreid has been trying to keep away from liquor - his wife is now in the temperance league - and has been taking injections. It's been having a peculiar effect on him however and with good reason.