Black Mesa Incident

"Those people, they're gone... because I did this."

- Vincent Stark, immediately following the Resonance Cascade. "Oh my God, this is crazy in a box with a side order of fries."

- Gordon Freeman, immediately following the Resonance Cascade.

The Black Mesa Incident, colloquially referred to as the Lambda Incident, was a catastrophic event that came about as a result of an experiment carried about by the Anomalous Materials department of the Black Mesa Research Facility.

The experiment triggered a Resonance Cascade, which allowed hostile alien life to invade the facility grounds via teleportation. Two specialized branches of the US military, the HECU (Hazardous Environment Combat Unit) and Black Operations are sent to the facility in order to prevent the incident from reaching the public eye by eliminating all parties involved. The incident came to an end on the 17th of May when the portal allowing the invading extra-terrestrials is closed, and the facility and everyone still present are destroyed by the on-site detonation of a nuclear bomb.

Prelude
Sometime prior to the incident, the research team at Black Mesa discovered the alien border world in the midst of developing teleportation technology. This border world is later referred to as "Xen."

Following its discovery, Survey Teams are sent on science expeditions to Xen by way of a large teleportation device deep within the confines of Sector F. The Survey Teams comb through the border world in the hopes of collecting data, flora, and even wildlife from Xen. One of the key sources of interest were the crystals present on the border world, dubbed "Xenium," as their unique properties would prove to be beneficial in Black Mesa's research and development of teleportation technology. Though the expeditions would prove to be a success with several samples and extra-terrestrial life now contained in Sector E, several research members stationed on Xen would later be killed by its inhabitants. At some point, Black Mesa scientists discovered Race X by chance when they opened a rift to another dimension during their portal technology experiments. As the nature and location of the dimension were largely unknown, the designation "X" was used by Black Mesa to refer to the dimension and its inhabitants.

In the days leading up to the Black Mesa Incident, a memo made by an employee with the initials L.M is sent to Colette Green (and cc'd to Isaac Kleiner) in which they state that, following extensive research done by Green, the sample dubbed "GG-3883" will replace the original chosen sample "EP-0021" in the coming experiment, as Green's research clarified the former's potency by way of purity.

Freeman's Mind
On the day of the incident, Dr. Gordon Freeman, the researcher who will be assisting with the experiment on the ground level, treats it as if it were any other day.

Upon pushing the test sample into the Anti-Mass Spectrometer, a resonance cascade begins to tear away at the test chamber as both Freeman and the science team begin to panic. The personnel overseeing the experiment are killed as beams of energy strike the room they are in, while Freeman finds himself trapped in the test chamber with no way to escape. After being teleported to multiple different areas on Xen, Freeman laments on the situation, referring to it as "crazy in a box with a side order of fries" before losing consciousness.

Stark's Mind
In an alternate timeline, Freeman bribes his former co-worker, Vincent Stark, into pretending to be him on the week of the incident, given the small resemblance between the two.

On the day of the incident, Stark voices his concerns over the potential safety hazards that come with pushing the Anti-Mass Spectrometer beyond its limits for the sake of experimental clarity. Upon pushing the test sample into the Anti-Mass Spectrometer, a resonance cascade begins to tear away at the test chamber as both Stark and the science team begin to panic. The personnel overseeing the experiment are killed as beams of energy strike the room they are in, while Stark finds himself trapped in the test chamber with no way to escape. After being teleported to multiple different areas on Xen, Stark loses consciousness.

Immediate Effects and Military Occupation
"I just overheard a secure access transmission." "Uh what..?" "Soldiers have arrived, they're coming to rescue us." "Oh? Finally! That's-" "Of course I have my doubts that we'll live long enough to greet them."

- A surviving science team member talking to Vincent Stark The Resonance Cascade had immediate and catastrophic effects, Xen creatures begin to relentlessly attack Black Mesa employees on sight. The Resonance Cascade also causes serious structural damage to the facility, with elevators collapsing and ceilings caving in.

Freeman's Mind
Freeman awakes in the test chamber with the Anti-Mass Spectrometer in pieces and sirens blaring throughout the ruined facility. As Gordon makes his way through what remains of Sector C, he discovers that some of the personnel survived the experiment, including Eli Vance, Vance tells Gordon that all the phones in the facility have been knocked out, and sends Gordon towards the surface to get help.

Stark's Mind
Stark awakes in the test chamber with the Anti-Mass Spectrometer and facility in ruins. As he makes his way through the remains of Sector C, he discovers that some of the personnel survived the experiment, including Eli Vance and Isaac Kleiner. Vance tells Stark that all the phones in the facility have been knocked out, and sends Vincent towards the surface to get help.

Meanwhile
Three survivors of the initial disaster, Dr. Gina Cross, Dr. Colette Green, and Dr. Rosenberg, make their way to the surface and call in the military to help them with the alien onslaught. The military, in the form of the Hazardous Environment Combat Unit, arrives quickly, deploying troops, ordnance, and vehicles via aircraft and trains. Aside from dispatching the aliens, these troops are also instructed to permanently silence the facility personnel who were witnesses.

The HECU's foray into the facility is initially successful. They manage to establish control of Black Mesa's surface facilities and began to make inroads into its extensive underground facilities, setting up several fortified outposts to keep the aliens at bay. They also manage to capture Dr. Rosenberg, who sent the distress signal and lock him in a railway cargo car for interrogation.

Barney's Mind
"Oh come on.. You suck, you all suck!"

- Barney Calhoun after the HECU trap him inside a boxar Barney hears a scientist calling from inside the boxcar and brings the boxcar out and into the freight yard. He opens the door and enters the boxcar to talk to the scientist, but HECU marines close the door behind him and lock him in. The scientist tells Barney that he is Dr. Rosenberg. He explains that he and a small team had been working on teleportation project for years and had planned on using the prototype labs housing teleportation technology, but were captured by the HECU. He tells Barney that if he can get him to the labs, they can use the technology to escape. Barney climbs through the vent in the ceiling of the boxcar with the help of the doctor and ambushes the soldiers outside.

After all the soldiers have been killed, Barney and Dr. Rosenberg make their way to the hallway nearby where Harold was found that is still under construction.

Freeman's Mind
"Okay I can understand shooting someone running at you screaming, but.. I don't know this feels shady."

- Gordon Freeman after witnessing a HECU Marine gun down a scientist. As Freeman makes his way towards the surface, he is told by surviving personnel that the military has arrived on the surface to rescue them. Gordon passes through the alien-infested Sector D Administration, and he finally reaches the Sector D High-Security Storage Facility, where the HECU has established a large presence. Shortly after arrival, however, Freeman witnesses a HECU marine murdering a scientist calling for help, revealing to him the true nature of the HECU's presence. Freeman fights his way through the military encampment and takes a service elevator to the surface, only to find that minor airstrikes have begun across the facility, and is forced to retreat back inside.

Stark's Mind
"But uh, the one thing I'm absolutely certain of is that you don't shoot the person you're trying to rescue.."

- Vincent Stark after witnessing a HECU Marine gun down a scientist. As Stark makes his way towards the surface, he is told by surviving personnel that the military has arrived on the surface to rescue them. He passes through the alien-infested Sector D Administration, and finally reaches the Sector D High-Security Storage Facility, where the HECU has established a large presence. Shortly after arrival, however, Vincent witnesses a HECU marine murdering a scientist calling for help, revealing to him the true nature of the HECU's presence. Stark fights his way through the military encampment and takes a service elevator to the surface, only to find that minor airstrikes have begun across the facility, and is forced to retreat back inside.

Meanwhile
"Hey what are you two doing here? Take cover, there are soldiers everywhere."

- A surviving security guard talking to Gina Cross and Colette Green. While HECU establishes their presence in the underground, Dr. Green and Dr. Cross, under the instruction of Dr. Keller, attempt to reactivate the damping locks to close the rift, but an alien force keeps it open. They then work to prepare the satellite delivery rocket for launch, which is essential for the work of the prototype displacement beacon, a device capable of reducing the effects of the Resonance Cascade. Cross and Green first find a living security guard who knows the all-clear codes needed to lift the military air-traffic lockdown. The two doctors then enter these codes, successfully lifting the lockdown and allowing the rocket to be launched. However, the launch is aborted when soldiers capture the control room and massacre its personnel.