When a storm forces Blackmer to stay at the house overnight, Culp decides to steal the theramine and sell it to the highest bidder. Waiting until the house's other occupants are asleep, he breaks into Orchard's laboratory and pours some theramine into a vial. The rest of the supply is accidentally knocked into a sink and drains into the Ambro River. When Blackmer and Culp leave the next morning, their boat is attacked by an alligator, now enormous due to the theramine contamination. Orchard's assistant, Hector McGill, manages to rescue Blackmer but Culp is nowhere to be found. The house is quickly surrounded by three giant alligators that repeatedly hurl themselves at the building with Orchard, Blackmer, McGill and the housekeeper, Mrs Files, trapped inside. At Mrs Files' suggestion, McGill transmits a distress call to International Rescue. This is picked up by John Tracy (voiced by Ray Barrett) on the Thunderbird 5 space station and relayed to Tracy Island, where Jeff (voiced by Peter Dyneley) immediately dispatches his other four sons to the danger zone in Thunderbirds 1 and 2. Arriving in Thunderbird 1 and transferring to a hover-jet, Scott (voiced by Shane Rimmer) fires the hover-jet's missile gun to disperse the alligators and accesses the house via the laboratory window. The room eventually caves in, forcing Scott and the others to retreat to the lounge. There, they are confronted by Culp, who holds them at gunpoint. Virgil, Alan and Gordon (voiced by David Holliday, Matt Zimmerman and David Graham) arrive in Thunderbird 2. Alan and Gordon man tranquiliser guns and subdue two of the alligators. When the third returns to the house, Alan exits Thunderbird 2 on another hover-jet to lure it away. He hits a tree and falls off the hover-jet, but is saved by Gordon, who tranquilises the alligator before it reaches Alan. Threatening to empty the entire theramine vial into the Ambro unless he is given safe passage upriver, Culp sets off in Blackmer's boat. At the same time, Gordon launches Thunderbird 4. A fourth, much larger alligator appears and attacks the boat, killing Culp. Virgil disposes of the creature with a missile fired from Thunderbird 2. Later, Gordon finds the theramine vial intact on the riverbed. After his sons return to Tracy Island, Jeff announces that theramine will be subject to international security restrictions. Tin-Tin (voiced by Christine Finn) has been away on a shopping