Fort Solis

The plot of the game follows an engineer, Jack Leary, arriving at the Fort Solis Mars base following an alarm call.[1] Following storm warnings however, Jack heads inside the base.

Jack Leary (Roger Clark) and Jessica Appleton (Julia Brown), scientists at a human Mars colony called Fort Minor, are preparing for an oncoming storm when they receive an emergency alert from the nearby mining station Fort Solis. Leary heads over to respond, where he discovers the fort on lockdown and no sign of the crew. His ability to navigate the station is initially limited due to the lockdown and his lack of security credentials. As he explores the base he encounters bloodstains and signs that he is not alone, eventually discovering several corpses of Solis crew members each inflicted with stab wounds.

Leary heads to the maintenance bay to restart the power generators, where he is attacked by Wyatt Taylor (Troy Baker), the lead officer of Fort Solis. Appleton, who has kept in contact with Leary over radio communications, heads over to Fort Solis at this time. Upon entering the base she immediately encounters Taylor, who attacks her but she is able to escape. Appleton begins exploring the base in search of Leary. As she investigates, Taylor taunts her over radio communications, trying to lure her to the station's greenhouse. While she explores the station, Appleton finds the remaining crew members deceased, each appearing to have also been murdered.

As they explored the base, both Leary and Appleton come across numerous video and audio logs from the crew members that piece together the events leading up to the lockdown. A growth accelerant appears to be causing plants at the base's greenhouse to die at an alarming rate. Taylor discovers this is caused by growing plants and food in Martian soil, which also infects them with a virus that spreads to humans upon consumption. As crew members begin to exhibit symptoms of the virus, Taylor alerts the agency in charge of the Solis operation, who ignore his warnings and ultimately suspend him from his duties. Seeking to contain the outbreak and prevent it from returning to Earth and causing a global pandemic, Taylor begins killing his colleagues one by one.

Appleton eventually arrives at the greenhouse, where she discovers Taylor and an unconscious Leary. Taylor notices that her hands are shaking, a symptom of the aforementioned virus, and severely wounds her. Leary awakens and attempts to carry Appleton to safety. Taylor catches up to them, and kills Appleton as she seals an airlock so Leary can escape. Leary walks through the storm outside into another building, where he has a final confrontation with Taylor. Taylor injures Leary, but is shot dead by agency forces that have finally arrived at Fort Solis responding to the alarm.

In an alternate ending, Taylor catches up to Leary outside in the storm, and they mortally wound each other in the confrontation. Both die either from bleeding out, or suffocating due to the breach in their spacesuits.

In a post-credit scene, Taylor is heard leaving a voicemail to his wife on Earth before he begins his murder spree. He warns her not to open a plant that he sent them from the station, and says his final goodbyes to his wife and daughters. However, it is implied that his message arrived too late and his family has already succumbed to the virus.