Secret Agent X-9 #5

Agent X-9 investigates a plot involving Dr. Stix and the Panama Canal zone, where a mysterious woman contacts him about a sabotage scheme. Dr. Stix, a mad scientist operating from a hidden laboratory beneath the canal, plans to commit murder and destroy the canal using explosives. After X-9 infiltrates Stix's underground lair and discovers his escape route, Stix flees into the canal zone, where he attempts to hide on a cliff but falls to his death. X-9 then reunites with Laura, a woman connected to Stix, and they escape together after a tense emotional confrontation about duty and love.