Colonel H.S. Stephens was a Colonial Marine officer who was a part of a Marine detachment sent to acquire a Xenomorph specimen for the Government. Stephens was an inexperienced commander, having spent much of his career behind a desk. For that he was not well respected by his troops or some of his fellow officers. Sometime prior to his leaving on the expedition, Stephens made a deal with an assassin named Massey, who worked for the Bionational Corporation on Earth. After selling out his troops to Massey and his crew Stephens was then shot and killed by Massey after holding up his end of the deal.
Colonel Stephens was working with a Terran Government scientist, Waidslaw Orona in acquiring a hostile species, the Xenomorph, for weapon development. They were tasked with getting ahold of an individual that had previous encounters with the creatures. There were three individuals that had encountered the creatures thirteen years ago. One was Ripley, who went MIA shortly after the encounter; another was Newt, who was institutionalized and the other, Dwayne Hicks, who was sitting in a prison cell on Earth. Choosing Hicks as the most suitable individual to lead, Orona ordered the imprisoned Corporal to be released and brought directly to MILCOM HQ from his cell.
When Hicks arrived, and having seen the blue box recording of The Dutton and the crew's encounter with a Xenomorph. Orona then asked the disgraced Marine for his take on the recording, Hicks sarcastically responded that the crew were lucky they were "blown to atoms when they did." Stephens already disliked the Marine's attitude and remarked thusly; that was when Orona asked him to tell his experience with the creatures. Stephens, already having his fill of Hicks' sarcasm, ordered the Marine to tell his experiences to the doctor. After that, Orona asked Stephens if he could have a moment privately with the Corporal; Stephens complied and Orona was able to talk Hicks onto the expedition. Sometime prior to mission preparations, Stephens was contacted by and made a deal with a man named Patrick Massey to sabotage efforts of the mission for his employers.
With the now promoted Sergent Hicks serving under Stephens, he took it upon himself to up the weapons from the standard issue M41E Pulse Rifles with Plasma Rifles. Stephens, furious with Hicks going above his head and interfering with his secretive sabotaging of the mission; ordered the plasma rifles off the ship and berated the Sergeant that his experiences have "warped his mind." Unknown to Stephens, Hicks still managed to smuggle miscellaneous components on board with the capacity to make a decent nuclear payload. Hicks also managed to smuggle an escapee from a mental hospital on The Benedict mere hours before lift off.
After The Benedict awoke the platoon and the support crew for the ship, Stephens then noticed the plus one on his roster. Having figured out it was Hicks going above his head again, the Colonel confronted the Sergeant in front of the platoon stating that Hicks could've screwed up the trajectory by readjusting the weight of the ship. Hicks replied that he made the necessary adjustments to the weight by dumping some raspberry-flavored rations. Still unfamiliar with the squad and unable to pick out the straggler Stephens demanded Hicks bring forward this "civilian advisor" for inspection telling the Sergeant to bring "him" forward. Hicks replied that it wasn't a "he" but a "she." Stephens, curious where Hicks got her asked the Sergeant and got the reply that he broke her out of a mental hospital.
After the platoon readjusted after spending nine months in hypersleep and went about their rounds on the ship, Stephens was prepping for Massey's ship to catch up and dock with The Benedict. While making a transmission to Massey, Stephens was discovered by a Marine on patrol duty. Before the Marine could react, Stephens ran a knife through the synthetic's throat, incapacitating him. The Colonel then put him in a space suit and spaced him with a timed grenade to finish the job. At some point during the trip to the planet, Stephens also sabotaged all of the Marines' weapons, storing the components in his quarters.
As Massey's ship closed in, Stephens was in the command portion near the proximity sensor when the Marine manning the station called Stephens over to report she had a reading on an incoming ship. Stephens, still maintaining his cover told the Marine to run a diagnostic scan to be "sure". The Marine ran the scan and reported that the systems were green. By the time the Marine turned around, Stephens drew his sidearm on her and shot her in the left eye killing her instantly.
After giving Massey the go-ahead on docking with The Benedict, the general alarm was sounded by someone who was suspicious when the ship docked. Still playing the role of commander, Stephens ordered the Marines to report to the dropship bay in full combat gear. After the announcement on the com, Hicks rushed in talking about an attack on the ship. Now revealing his true colors, Stephens drew his sidearm on Hicks and told him not to make any announcements on the com and led the Marine to the pirates' entry point.
When Hicks and Stephens made it to the hatch that the pirates were entering from Stephens was greeted by Massey. Hicks, angry over being betrayed, berated the traitor for his actions. Stephens stated that he did this to ensure his future. Massey then asked the Sergeant to move aside, which Hicks complied with. Stephens then found himself staring down Massey's gun, pleading with the mercenary, exclaiming that he had made a deal with the assassin. Massey replied that a commander who betrayed his troops was not fit for command and fatally shot Stephens in the chest. Stephens' remains along with the other Marines that resisted and died were spaced by the pirates.