A swamp ghoul emerges from the depths of the laser-generated swamp.

Be prepared to be scared. Very scared.

The ominous collection of black containers on Palmerston North's Railway Land is home to a Halloween shriek-fest as hundreds pay to undergo a fright experience.

Nightmares' Halloween show is back, and this time owner Hamish Williams said it's a haunt extravaganza on steroids.

MURRAY WILSON/STUFF Splattered dolls in the nursery wing of the Nightmare containment Haunted House.

"It was fantastic. People come out panting, sweating and giggling. It's really cool standing at the exit and seeing everyone's reactions," Williams said.

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Narrow passageways, tight corners, claustrophobic spaces, hidden doorways, special effect lighting and sound, blood splattered decor, authentic props and 18 ghoulishly costumed and hidden actors seemed to meet most expectations of a decent heart-stopping fright.

MURRAY WILSON/STUFF Stabby, The Joker, and Jacko the Clown are all part of the frightening fun at the Nightmares halloween attraction.

Plenty of people enjoyed the open-air scare corral at Halloween in 2016 when Williams resurrected the former Marton Haunted Maze in downtown Palmerston North.

"Last year, visitors to the attraction exceeded expectations in their hundreds."

That was despite less than favourable conditions.

"The weather affected things last year, so this time we've thought outside the box by putting everything inside the box."

Williams had spent the intervening 12 months devising a whole new terror-inducing encounter. The Nightmare Containment Haunted Attraction takes place inside four 40-foot shipping containers.

"Last year was pretty much a trial concept. Its success gave us the confidence to take things to a whole new level."

Being inside meant there was much more control over the environment, lighting and atmosphere. Among the features is a squeeze room, a laser-created swamp, and a glo-room laboratory.

"It'll be the ultimate journey of fear."

Williams said he regularly travelled to the United States for inspiration, and had sourced the detailed props from there.

"Two builders and a set designer have worked on this for 12 weeks."

There are options for people with restricted mobility, emergency exits in case things become a little too intense, while a medic and security staff will be on duty.

The attraction was designed to be easily moved and could be set up in other towns.

"We'd like to be doing four or five shows a year," Williams said.

Actor Jacob McDonald said the haunted house was scary enough for the performers during their familiarisation session, even when they knew what was going to happen.

Not recommended for under-10s, with under-16s accompanied by an adult, Nightmares has its last night tonight, from 7.00pm until 10.30pm, with details on nightmarecontainment.com and on Eventfinda.