Thunderbirds Are Go Episode 20 The Hexpert Episode Title:The Hexpert.Episode Description:A scientist accidentally locks herself inside a vault housing a destabilizing anti-matter reactor. There is only one person who has successfully broken into a vault like this before - Parker. Colonel Casey of the GDF recruits Parker for the job, but moments after getting through the outer vault door, both he and Lady Penelope become trapped as well. Virgil and Scott must transport the vault to an isolated area on Thunderbird 2, while Parker and Penelope must try and free themselves and the scientist before the anti-matter explodes.