A timely reminder that when The Evil Within is good it is very good, The Assignment is a welcome return to Mikami's latest horror universe. A focus on stealth initially grates, but soon reveals itself to be a useful way for Tango Gameworks to go beyond worries about ammo counts and match useage, instead building out on the game's psychological horror.

A side-story that crosses over with the events of the main campaign, The Assignment pits players as Juli Kidman, formerly one of the supporting cast. Her story is initially one of subterfuge, as she infiltrates main character Sebastian Castellanos' team in a bid to recover Leslie, whose mind holds the key to the STEM system (a version of the Matrix which feeds off of fear, essentially) they're all trapped in.

Her employers are standard shadowy bad guys, led by the Cigarette Smoking man's younger, taller brother. Most of the early going is sub X-Files stuff, but as Kidman starts to rail against her employer and her own psyche is raided for leverage, The Assignment kicks into gear.

Kidman has no firearms (outside of a short set-piece), instead relying on distraction and lures - thrown bottles, shouting, even prank phone calls - to get by enemies. Initially it can frustrate: while the geometric nature of your environments (think some of the quieter moments of FEAR) provide ample items to hide behind and manoeuvre around, she takes just that little bit too long to leave cover after you've alerted your foes. This is due to the game giving you a little speed boost when holding a direction and exiting cover: great for getting away quickly in a panic, but it often leaves you unwieldy for a few moments, exposed when you least need it.

As The Assignment goes on, however, these frustrations minimise. So too does the reliance on labs and other boring environments as backdrops, instead taking a turn for the dank and gothic as Kidman's loyalties divide. It's here that the DLC plays to the main game's strength: mainly, that Mikami really knows how to do dread.

He and his team know that there's a stillness, an anticipation mixed with surreality, that informs the best psychological horror, and here - no doubt buoyed by the excellent engine and grimy, widescreen, underlit aesthetic - Tango exploit it expertly. There are whole stretches where little happens, in terms of enemy encounters. Instead, Kidman's tough exterior starts to unravel, and the environments change to reflect that.

Grotty sewers, dilapidated surgical wards, and shapeshifting environs have all been done before, and most of these wouldn't look out of place in any of the Silent Hill games. But it's the exploitation of the fact that everyone - the player, the character, the director - know they're in what is in essence a twisted, deadly simulation that gives the game its eerie edge. There's no dissonance here, and that the player and Kidman's goals and fears are intertwined gives The Assignment an interesting flavour.

As does Kidman's relative weakness, and the solutions she has to find to survive. With no guns, Tango can't rely on straight up combat to pad the action, nor can it just toss in boss battles, which were some of the weakest elements of the main game anyway. Instead, various puzzles stand in. None of them are particularly difficult: rerouting electrical boxes, or using your flashlight to open hidden doors. But all of them take that bit longer than you'd like, driving up the tension.

A lot of enemy encounters happen just after you've found the solution to escape your most recent prison, resulting in interesting cat and mouse moments as players flee overmatched opponents. A particular highlight is a boss character with a gigantic searchlight for a head, which is also hunting for Leslie and has no qualms about killing you in the process. Resembling Bioshock 2's Big Sister in both aesthetics and movements, it's a constant thorn in your side and, as such, a pleasure to finally take down.

At around two hours long, The Assignment is a reasonably-sized add-on which fleshes out The Evil Within's story while building on what made it so enjoyable in the first place. Let's hope its follow-up, The Consequence, lives up to it.

Version Tested: PlayStation 4.