Detective Comics #242

From 1957, this tenth-cent DC thriller puts the Dynamic Duo in a genuinely unnerving spot: a smirking gangster in a white coat threatens to expose Batman as Bruce Wayne while his criminal cohorts gloat over having seized the Bat-Cave as their own secret headquarters. Batman and Robin stand their ground on the right side of the cover, framed against what appears to be a vault door, while the villains brandish their leverage with gleeful menace. Sheldon Moldoff's cover art captures that perfect Silver Age tension — the heroes composed and defiant, the crooks certain they've already won — making "The Underworld Bat-Cave!" a wonderfully suspenseful snapshot of Batman at his mid-century best.