Baffling Mysteries #5 is the debut issue of Ace Magazines' second flagship horror anthology, cover-dated November 1951 and published bi-monthly at $0.10 under the Periodical House, Inc. imprint. Despite being numbered #5 — the series continued the cover numbering from the prior title Indian Braves — it is the first issue to bear the Baffling Mysteries title. The 36-page full-color issue opens with "Volcano of Vengeance" (pencils: Mike Sekowsky, inks: Vince Alascia), in which North American Museum field agent Tod Sloane investigates Mount Pataxo in Central America and discovers a subterranean volcanic cult of immortal goat-men; "The Lady Was a Tiger" (Ken Rice) follows big-game hunter Stuart's wife as a deranged jungle doctor injects her with tiger blood, transforming her into a predator who ultimately kills the doctor herself; "Terror in the Coal Pits" (pencils: Gene Colan) rounds out the confirmed stories, with Nurse Jarvis encountering the ghosts of miners lost in a cave-in ten years prior. An additional ski-jump horror story (Irma Monroe) is also documented in the GCD entry. Lettering throughout the issue is typeset (Leroy lettering), consistent with the early Ace house style.

Ace Magazines published horror titles including Baffling Mysteries, Hand of Fate, and Web of Mystery, and a number of Ace stories were used as examples of violent and gruesome imagery in the 1950s US Congressional inquiries into the influence of comics on juvenile delinquency that led to the Comics Code Authority. Operating through Periodical House Inc. and numerous related imprints, all controlled by publisher Aaron A. Wyn and his wife Rose Wyn, Ace positioned Baffling Mysteries as a companion title to The Beyond (launched November 1950) and Web of Mystery (also 1951), making 1951 Ace's most horror-intensive publishing year. The series attracted an exceptional roster: Mike Sekowsky, Lou Cameron, Gene Colan, Maurice Gutwirth, Jim McLaughlin, Ace Baker, Bill Molno, Chic Stone, and Ken Rice contributed stories across the early run. Unlike EC Comics' more graphic approach, Ace horror tended toward psychological and supernatural themes with somewhat restrained violence — a quality that, together with its better-than-average art, has earned the title an enduring critical reputation.

Today, Baffling Mysteries #5 stands out for two reasons beyond its own content. First, it marks the career debut of several Golden Age artists in a horror context — most notably the early freelance work of Gene Colan, who would become one of Marvel's defining horror artists two decades later with The Tomb of Dracula. Second, the complete Baffling Mysteries series is freely available as confirmed public domain through Comic Book Plus, making it one of the most accessible mid-tier horror anthologies of the pre-Code era. Modern collectors prize #5 as the key first issue of the run, with the PS Artbooks reprint series (Pre-Code Classics: Baffling Mysteries) drawing fresh attention to its rich creative roster.