Rookie caver Kevin leads an expedition into the depths of a Tennessee cave. Three hopefuls compete for a high-flying position with the Sonoma-Marin Tree Men, and novice flyer Ron travels to South Africa to take a rigorous bush pilot course.
Rookie tree climber Sean jeopardizes his team when he ignores expert advice about scaling a redwood. Novice commercial divers Dan and Erik attempt a dangerous underwater welding job to repair a submarine in San Diego, and amateur pilot Ron gets his first taste of canyon flying.
Hoping for a job as a commercial diver, Erik welds a patch on a sunken submarine, but his breathing spirals out of control. Rookie heavy haul driver Fred drives through a hurricane, and three lessons into his bush pilot training, Ron ends up in the hospital.
Rookie diver Erik struggles underwater while rigging a sunken yacht. Heavy haul trucker Fred attempts to transport a 105-ton crane through a hurricane, and novice tree man Nate drops a large, dead eucalyptus tree nicknamed the Widowmaker.
Rookie tree man Tomas freezes in fear halfway up a redwood, and greenhorn diver Erik descends deep into the ocean to collect research samples. Aspiring volcanologist Sarah attempts to scale an active volcano and assist in thermal mapping the crater's eruptions.
Volcanologist Sarah continues her first expedition on an active volcano. Rookie tree men Nate and Tomas face off in their most difficult challenge yet, and greenhorn wind tech Mike attempts to scale a 120-foot wind turbine.