Providing a glimpse into the external underground network that helps Hogan's Heroes ferry escaped Allied prisoners of war out of Germany and back to Britain, "The Flame Grows Higher" also hints at the dangers inherent in such an operation, particularly after an American airman, Captain Warren (Jerry Ayres), whom the Heroes helped to escape is brought into Stalag 13 after being captured somewhere along the network route, with Heroes leader Colonel Hogan determined to locate the security breach--and close it.
Writer Laurence Marks helped David Chandler and Jack H. Robinson script the story they created that requires a ruse to get the Heroes out of camp long enough to trace the route. That ruse is a "forest fire" that Sergeants Carter and Kinchloe set near the camp, enabling Hogan to volunteer his men to commandant Colonel Klink to fight it--provided they are escorted by guard Sergeant Schultz, of course. It's a flimsy premise--the "fire" barely qualifies as a barbecue and the Heroes run rings around the hapless Schultz including the theft of his truck--but it gets Hogan and Corporals LeBeau and Newkirk to the tavern run by Eva (Susanne Cramer) and Margit (Hannie Landman), two blonde bombshells who delight woman-starved LeBeau and Newkirk, that acts as the traffic hub for this segment of the escape route.
Also on the escape route are Willy (Charles H. Radilak) and Jenny (Irene Tedrow), an older couple who run a farm near the tavern whom Hogan suspects of being the turncoats, particularly when Hogan discovers SS uniforms in their closet, with LeBeau and Newkirk willingly disobeying Hogan's order not to come after him if he doesn't return promptly adding to the episode's tensest moment. With a cheeky yet generally plausible blend of farce, danger, and sex appeal, "The Flame Grows Higher" delivers an involving story with a credible peek at how life outside Stalag 13 affects what happens inside the camp.