Half-Life: Decay storyline
This article describes the Half-Life: Decay storyline, mission by mission.
Dr. Cross and Dr. Green are members of a different team in Black Mesa than Half-Life's protagonist, Gordon Freeman. They are responsible for monitoring the equipment which Gordon uses during the experiment, and are in turn monitored by Dr. Rosenberg and Dr. Keller. Like Freeman, they are forced to fight for survival in the aftermath of the Resonance Cascade.
 Mission 1: Dual Access
This is the only mission in which the G-Man is seen.
 Mission 2: Hazardous Course
 Mission 3: Surface Call
Cross, Green, and Rosenberg reach the surface, with the objective of accessing the Satellite Communications Center to contact the military, as Rosenberg hopes that they will secure the facility and escort the personnel to safety. However, they find the front door to the Comm Center locked, forcing Cross and Green to circle around through nearby warehouses to get to the unlocked back entrance. Once inside, they manually align the satellite dish and Rosenberg successfully contacts the military while Cross and Green head back down to Sector C.
 Mission 4: Resonance
Cross and Green return to Anomalous Materials and link back up with Dr. Keller. Dr. Keller decides that the best course of action is to re-engage the dampening fields, which he felt would end the Resonance Cascade. To do this, Cross and Green travel through the facility and successfully reset the secondary and primary dampening locks. However, the dampening fields fail soon after. Keller discovers that the failure was caused by intentional interference from the other side of the rifts and realizes that not all the aliens might be there by accident.
 Mission 5: Domestic Violence
Keller hatches a plan to create a resonance reversal using the prototype displacement beacon in the Gamma Labs. However, he needs a satellite in orbit before he can go through with the plan. Personnel in the High Altitude Launch Center are ready to launch the satellite, but due to a military air traffic lockdown that is in effect they can not. To remove the lockdown, an all-clear code is needed. Keller, Green, and Cross use the transit system to get to the nearby Level 3 Dormitories. There, they begin searching for a security guard with the codes. Their task is made more difficult by the fact that HECU soldiers are also present, and are busy eliminating science and security personnel. Eventually, the security guard is found. Armed with the codes, Cross, Green, and Keller travel to the Black Mesa Air Control facility on the surface.
 Mission 6: Code Green
Cross and Green, after several fights with HECU soldiers and after successfully fighting off an Osprey Heliplane, manage to secure the Black Mesa Air Control building. They proceed to enter the all-clear codes and lift the military air-traffic lockdown. They then return to Keller and head back underground to find a way to the Gamma Labs.
 Mission 7: Crossfire
The next task for Cross and Green is to manually raise the prototype displacement beacon in the Gamma Labs to the surface, so it can be activated. Keller reaches the main lab area, but cannot raise the beacon from where he is because of an obstruction. After accessing the labs via the drainage canals, Cross and Green travel through the lower levels of the labs, encountering battling HECU soldiers and Xen creatures as they go. They reach the beacon, clear the obstruction blocking it from ascending, and then raise it successfully.
 Mission 8: Intensity
Cross and Green return to Keller in the lab control area, where he gives them the task of activating the beam matrix system, which provides the power required for the prototype displacement beacon. To do this, they first take an elevator up to the Alien Quarantine Labs, which have become overrun by Xen creatures. After navigating through the labs, they reach the beam matrix and attempt to activate it while simultaneously defending it from Vortigaunts and Grunts, who are rapidly teleporting in. The beam matrix is activated, and Cross and Green return to Keller, who is making the final preparations for the resonance reversal.
 Mission 9: Rift
Cross and Green are forced to defend the displacement beacon against a variety of attacking Xen creatures, including an Alien Craft. In the midst of the battle both characters are caught in what is explained as a "harmonic reflux" by Dr. Keller. It is during this sequence that the voice of Dr. Rosenberg can be heard warning that he "can't keep the portal open much longer," alluding to Calhoun's coinciding trip in Xen during Blue Shift. Dr. Cross and Dr. Green then return safely and Dr. Keller congratulates them on their success.
The resonance reversal presumably had the effect of severely weakening the resonance cascade. It still remains unclear whether the doctors managed to survive the nuclear explosion that occurs at the end of Opposing Force.
 Bonus mission: Xen Attacks
It is the bonus mission of Half-Life: Decay. In it, two Vortigaunts named Drone Subjects X-8973 and R-4913 must retrieve the crystal sample which was used in tests (and stolen by the G-Man) in Black Mesa and take it back to their leader Nihilanth. It is also interesting to note that the level itself is connected to the parking garage as seen near the end of Half-Life: Opposing Force where the Nuclear warhead is disarmed by Adrian Shephard and rearmed by the G-Man.
In order to unlock the Bonus mission, an A-grade is required on all 9 of the other missions.
 See also
- Locations in the Half-Life and Portal universe for Half-Life: Decay
- Cut missions from Half-Life: Decay
|Half-Life story arc||Half-Life storyline · Half-Life: Opposing Force storyline · Half-Life: Blue Shift storyline · Half-Life: Decay storyline|
|Half-Life 2 / Portal story arc||Half-Life 2 storyline (original storyline) · Half-Life 2: Episode One storyline · Half-Life 2: Episode Two storyline · Portal storyline · Portal 2 storyline|
|Overall||Half-Life and Portal universe · Timeline of the Half-Life and Portal universe · Canon · Recurring themes · Retcons|