"The Mark of Cain; or, Nick Carter's Air-Line Case" edited by Chickering Carter is a serial detective story written in the early 20th century. This installment features the renowned detective Nick Carter, who is drawn into a case that intertwines with the mysterious and tense circumstances surrounding a young telephone operator named Helen Bailey and her criminal brother, Bart. The narrative unfolds as Nick grapples with his intuition and the clues surrounding a series of robberies, while also attending to the personal plight of Helen. The opening of the story establishes a suspenseful atmosphere, as we are introduced to Helen Bailey at a switchboard, whose expression reveals her distress as she listens to a phone conversation that leads to her fainting. Nick Carter witnesses this and comes to her aid, but their interaction hints at deeper secrets she's unwilling to share, particularly concerning the fate of her brother. Following this, we learn of Bart Bailey's criminal activities, which entangle Helen in a police investigation, heightening the stakes for Nick as he sets out to protect her while investigating a significant theft from a nearby department store. The initial chapters effectively set the stage for a thrilling investigation interwoven with personal drama, as Nick Carter showcases his analytical prowess and compassion in a world rife with deceit and danger. (This is an automatically generated summary.)

Nick Carter Stories No. 148, July 10, 1915; The Mark of Cain; or, Nick Carter's Air-line Case