Cheng-Ying Lai (uncredited)
Godfrey Ho was the king of what many refer to as the 'cut-and-paste' technique of filmmaking. Meaning, he'd get his hands on someone else's movie, eliminate some of the footage, add a bit of his own and then re-edit and re-release it as a brand new feature (the much-hated Jerry Warren operated in about the same way in America). Knowing that many Asian films would never be released to Western audiences, Ho would have them English-dubbed (often completely changing the plots in the process), hire a few Caucasian actors to interject into the works (in scenes which usually had absolutely nothing to do with the original film) and then release the finished product to the unsuspecting public through Joseph Lai's company IFD Films and Arts Ltd. The vast majority of these were martial arts films, but Scorpion Thunderbolt was one of their few horror releases. Most of the footage is from Cheng-Ying Lai's Snake Woman, a Taiwanese production filmed back in 1983. From all indications, that film was barely released in Asia (I don't buy that is was never released like some claim because there's a poster), let alone anywhere else, which made it the perfect victim for Ho / Lai's predatory 'style.'
The bulk of Scorpion (also released under the generic but more fitting title of Snake) is the 'borrowed' film, which revolves around female reporter Helen Yu (Juliet Chan). Helen seems like a meek and sweet enough lady, but every once in awhile she transforms into a vicious snake monster and hits the streets looking for victims. Some blind man roaming the streets plays a song on a flute that makes her transform. A flashback reveals that Helen's mother was the daughter of a snake killer who fell in love with "The Prince of the Snakes;" a coupling that resulted in a baby who bites off mom's tit while nursing and caused her grandfather to throw a hatchet into his daughter's back! The city's miserly police commissioner is baffled as to what's going on, but assigns two of his best inspectors; Jackie Ko ("Bernard Tsui" / Shou-Ping Tsui) and his female partner Inspector Li ("Nancy Lim" / Nan-Shi Lin) to the case. Li has fallen in love with Jackie, so she doesn't quite like it when her partner finds himself falling for Helen. A love montage (frolicking on the beach! eating freshly caught fish right off the skewer at a lake!) later, Jackie is head-over-heels for the mysterious beauty, but will his love remain once Helen's beastly side is revealed?
The newly added footage features one-time peplum / western actor Richard Harrison. The middle-aged, washed-up Harrison was also the 'star' of many other productions for the same company. In fact, director Ho got maximum mileage from the actor and the scenes the company shot with him would later be recycled for many other IFD productions. Harrison's character, named Richard, is first seen cruising down the road. He picks up a female hitchhiker who flashes him and accompanies her back to a movie theater for a private screening of a porno she's starring in. After doing a strip tease set to Jean-Michel Jarre's 'Oxygene' (!!) she tries to stab Richard during sex, pukes up some orange stuff and dies. Other henchmen will show up to try to take Richard out and they're all being sent by a witch ("The Queen of the Scorpions") who plays around with frogs and eels, constantly beats on a drum, wears sharp silver blades on her fingers and seems to be controlling all of the action. She wants a ring that Richard owns that can be used to destroy her. These witch scenes don't appear to come from Mongnyeo han, but they also don't match up with the Harrison footage, so it's hard to tell just what they were taken from.
Ignoring Ho's newly added footage, the hack job editing and the abysmal dubbing, Snake Woman appears to have been a hokey monster movie, but sincere and somewhat charming all the same. There are definitely some fun scenes in here, including a hilarious attack on some teenage girls (one in the shower), some disco dancing and a finale featuring the snake woman leaping out of a building and flying around while a squad of police officers try to shoot her down. Some subplots don't seem to have much to do with anything. There's an escaped criminal who attempts to kill Jackie (and rape his partner) but then just disappears, a madman who kills a cat and throws its guts at a hospital staff (??) and another scene of a drunk tying his unfaithful, hairy-armpitted wife up spread eagle and shooting pool balls at her crotch! One of the better horror-oriented scenes finds Jackie and Helen trapped in a moving car being overtaken by snakes. The rubbery creature design (which is difficult to see until the end) is pretty ridiculous, but there's plenty of blood and gore in here, as well as a generous amount of nudity.
Not only utilizing footage from possibly two other films, this one also swipes snippets from Pino Donaggio's Carrie (1976) score to help fill out the soundtrack. The copyright date in the credits is 1985, but the film wasn't released until 1988. It has been issued on both VHS and DVD (on Videoasia's "Tales of Voodoo, Vol. 5").