SG-1 returns through the Gate with a strange energy-emitting device and soon sees mysterious incorporeal bug like creatures. The creatures are harmless and exist normally on Earth but the device conveys the ability to see them...and it's contagious.
O'Neill spreads the "plague" to a small town en route to his fishing vacation. Sam and Jonas come up with a cure but Vernon Sharpe, a military vet and garage attendant who is rather paranoid of the government since being in the Gulf War, escapes the quarantine. The team tracks Vernon through his mother and Jack confronts Vernon in an abandoned hanger and convinces him to help his country by keeping the secret.