The Missing Link is the first and only add-on for Deus Ex: Human Revolution, developed by Eidos Montréal in co-production with Square Enix and was announced in October 2011. In North America and Europe, it was released on October 18th. The add-on was available on PS3, Xbox 360, and PC, but would later be ported to OSX and Wii U.
The Director's Cut comes with the Missing Link integrated into the storyline.
The Missing Link explains what happened to Adam Jensen during his three-day disappearance after he left Hengsha a second time. Waking up tied to an electromagnetic chair that inhibits augmentations, Jensen bears the torture of the base commander, Netanya Keitner, who believes he is a spy. After the electromagnetic chair strangely deactivates in Keitner's absence, Jensen attempts to escape.
Sneaking his way through the ship, Jensen is briefly contacted by a mysterious man over his radio, who then gives him directions to his equipment. After regaining his vest and passing through several areas, Jensen then escapes the ship when it docks at an oil rig owned by Belltower, and is told by his mysterious contact to rendezvous with a mole. Upon reaching the rendezvous, it is revealed that Keitner is a double agent working for Interpol, which is attempting to gather evidence on Belltower. Keitner then tells Jensen that she was the one who released him, and that he will need to help her gather enough evidence to incriminate Belltower.
Making his way through the detention blocks filled with kidnapped innocents being held prisoner, Jensen eventually overhears Pieter Burke, the augmented commander of the base, telling scientists Gary Savage and Tiffany Kavanagh to continue research in a hidden lab. After stealing one of Burke's spare prosthetic eyes, Jensen uses it to gain access to the lab with the help of Keitner's friend Garvin Quinn. Descending into the underwater lab, Jensen confronts Dr. Kavanagh, who agrees to testify against Belltower in exchange for protection.
After heading back up to the base, Keitner learns that Burke has discovered their plan, is fatally wounded in a firefight with several soldiers, and dies shortly after Jensen reaches her. Burke then begins to flood the underwater base and the prison cells with toxic gas to remove any potential witnesses. With the option of diverting all the gas to one of the two areas, Jensen is then forced to either save hundreds of lives or the only person who can testify against Belltower. A third, hidden option is present: by accessing a vent in the nearby area, Jensen can destroy the gas dispenser, saving both parties.
After saving one or both of the targets, Jensen then makes his way to Burke, and he is given the choice of killing or sparing him; regardless, the mysterious man contacts him again and tells him another ship has been found that will take Jensen directly to Megan Reed's location. Upon reaching the dock, it is revealed that Jensen's mysterious contact is actually Quinn, who explains that he hired Keitner under the guise of an Interpol agent, and that he was withholding the truth from both Jensen and Keitner to use them as pawns against Belltower and, by extension, the Illuminati. Quinn then proceeds to either commend or question Jensen's actions with the gas choice, before placing him back in a cryosleep pod.
After Jensen re-enters cryosleep, he is airlifted to the ship by helicopter as Quinn discusses Jensen's potential use as an ally with his superior, Janus, only to be dismissed due to Jensen's obsession with Megan.
- At the beginning of The Missing Link, Adam is stripped of his use of his mechanical augmentations (and all other augs) allowing the player to remake Adam with up to 7 beginning Praxis kits, minimum of 5 Praxis kits
- The new environments in the add-on feature improved lighting effects as well as upgraded weather effects such as rain
- Add some new elements to the main plot
- New characters linked to the main plot
- New environments
- New shirtless "outfit" for Adam Jensen during the add-on
- 10 new achievements/trophies (Wii U, Steam, XBL, and PSN achievements)
- A golden revolver for Adam (fully upgraded and if you don't find it during the mission, it can be taken from Burke at the end)
- The topmost left stasis pod in Hei Zhen Zhu's forward cargo hold has a woman named RZZRGRRL with specular eye implants and titanium implants under her fingertips. This is clearly an homage to Molly Millions the Razor Girl, one of the main characters of Neuromancer, the Cyberpunk Manifesto by William Gibson.
- In another pod, players can read about the descendant of some people stranded on an abandoned island, coordinates around 10°S 110°E. The coconut radio and bamboo artifacts are references to Gilligan's Island.
- A book near Quinn's shop talks about skull guns, a reference both to the Diamond Age by Neal Stephenson and to Gunther Hermann from the original Deus Ex.
- Upon activation of the CASIE mod on Quinn at the end of the game and following further questioning, he refers to the misappropriation of the term 'invisible war', perhaps hinting at the mixed opinions regarding Deus Ex: Invisible War.
- Occasionally, when asking Quinn to enter the shop, he will say "What are ya buying". This is a reference to Capcom Productions game Biohazard 4 (Resident Evil 4). In the game, the protagonist, Leon S. Kennedy, encounters an NPC called the Merchant. He acts in a similar way to Quinn, providing the player character with weapons and upgrades, as well as a place to sell items acquired.
- Numerous references to Joseph Heller's book Catch-22 can be found in throughout the game. Examples include e-mail logs for a Requisitions Officer by the name of Milo M Binder.
- An e-mail on Milo M. Binder's computer makes a reference to the supply needs of the Belltower base. Near the end and in the reply is a reference to ordering a pizza oven by utilizing an S-1798 form and writing "pizza oven" where it says "machine gun." This is a reference to M*A*S*H (Season 2, Episode 12) where a weedy Supply Captain won't let the 4077th have an incubator, but references the pizza oven instead.
- Another reference to M*A*S*H can be found in an e-mail from Cpl. W. O'Reilly to Milo M. Binder. Cpl. O'Reilly is better known as "Radar" O'Reilly.
|"Gamers will be able to experience a vulnerable side of Adam like never before, which gives the overall game a whole new dimension. 'The Missing Link' propels players into compelling gameplay, beginning with Adam being temporarily stripped of his use of augmentations; new, visually stunning environments; and the continuation of Deus Ex: Human Revolution’s conspiracy-rich story."|
|— David Anfossi|
For the details on missions, experience, achievements, and collectibles, please go to The Missing Link walkthrough page.