Iconic sci-fi series The X-Files may be dividing long-time fans with its modern revival. But most would agree that when it first hit screens 25 years ago, it was gripping, essential TV.
A big part of the early seasons' success were the frightening 'Monster of the Week' episodes. And a certain animal control officer named Eugene Victor Tooms was the very first - and arguably most infamous - of those monsters.
The mutant serial killer had viewers everywhere double-checking the corners of their rooms. And under the toilet seat.
It all begins with a locked room mystery.
In the opening of classic episode 'Squeeze', a businessman is found brutally murdered in his office, his liver apparently ripped out by someone's bare hands.
But there are no conceivable entry points that the killer could have come through, or escaped from. Other than a tiny vent in the wall, that is.
Throughout the episode, grisly details emerge
Mulder and Scully are brought in to help investigate, and soon link the case to other inexplicable slayings 30 years apart; in 1963, 1933 and as far back as 1903.
The plot thickens. Creepy suspect Eugene Tooms is caught climbing through an air duct at a crime scene. And Mulder, to his colleagues' all too typical disbelief, begins to theorise that the man is something not quite human.
Later, we get the proof for our own eyes. Stalking his latest victim, Tooms contorts and bends his body in order to fit down a chimney, like a nightmare Santa Claus (hence 'Squeeze').
Ultimately, Scully only just avoids meeting the same sticky fate.
Throughout the episode, grisly details emerge.
Tooms, it seems, is an immortal creature; capable of hibernating for generations at a time before returning to kill again.
All he needs to fuel his unnaturally long life is a stock of human livers - and a nest made from paper and bile.
You're never safe
It's not hard to see why Tooms makes for such a terrifying villain. And why, in unusual fashion for The X-Files, he returned for a second outing that very same season; with Mulder and Scully confronting him once more in an episode simply titled 'Tooms'.
The unnerving performance of actor Doug Hutchison, with his intently staring glowing eyes, almost perennially silent demeanour and patient, sly cunning, gives him the sense of a lizard-like predator in human form.
There's also a touch of Hannibal Lecter with Tooms' appetite for human livers, and a hint of horror tale IT with his ability to hibernate and return every three decades.
Doug Hutchison as Tooms, lying in wait (Photo: FOX)
But it is the concept itself that so unnerves. The thought of a cold-blooded killer who can get to you regardless of where you are. Clambering through vents and tiny windows, under doors and cracks, and lurking in your car boot. Or in your U-bend...
With Tooms around, you're never truly safe.
Hutchison fought "tooth and nail" to wear the contact lenses that gave Tooms his trademark "bile-like, yellow eyes", after the producers were going to axe them
'Wonderful, weird character'
Conceived by Glen Morgan and James Wong for the show, the writers had the idea when they were working late - and thought how horrifying it would be if something climbed through the nearby vent.
Digital effects were used for certain 'stretching' moments in the initial episode, while a contortionist was used for the chimney sequence.
Years later, those popping noises as Tooms' joints dislocate remain disturbing.
In interviews, Hutchison has described Tooms as a vampire-like individual: intelligent, instinctive and driven purely by need.
He has also pointed to the importance of 'stillness' in his performance, which definitely helps add to the uneasy atmosphere. Even him sitting on a bed, looking to the open 'letterbox' on his cell door, is terrifying.
'Tooms' was also the instalment that introduced viewers to Assistant Director Skinner, making it an important episode all-round
X-Files creator Chris Carter decided to bring the "wonderful, weird character" back in order to give audiences another scare before season one came to an end.
And it proved to be an inspired choice.
Villain of the year
Mulder's tense, nail-biting flight from his nemesis at the climax of 'Tooms' was given real-world weight by the fact that Hutchison insisted on filming the scene naked.
Lathered in cake frosting mixed with yellow food colouring, no less.
"It made the scare, the creep, all that more real," said Carter.
The impact of the character on the popular consciousness was instant. Back in 1993, Tooms was voted 'Villain of the Year' in a poll. But his notoriety has not faded with time.
Fantasy author Neil Gaiman named the character one of his all-time favourite monsters. Critics have regularly praised 'Squeeze' and 'Tooms' as early high-points in The X-Files mythology.
David Nutter, who directed the latter, recently received an Emmy Award for his work on Game of Thrones.
Morgan and Wong went on to work on the Final Destination movies, while Wong has also played a key part as a writer and producer on hit TV show American Horror Story.
Hutchinson would later team up with them both on post X-Files projects, including Millennium and Space: Above and Beyond.
In an interview, Hutchison once joked that: "Tooms is alive and well and hibernating in a nest of bile somewhere".
It's been 25 years since Tooms troubled our screens. So if he really is out there, it's almost time for him to strike again...
The X-Files season one, including 'Squeeze' and 'Tooms', is available for free to Amazon Prime Video members in the UK.
• Have your say on the latest TV with Screen Babble, the television discussion group on Facebook.
This article originally appeared on our sister site, iNews.