An engineering prodigy, Isaac is the son of Paul and Octavia Clarke. As a celebrated ship architect, Paul was often on assignment away from home, leaving Isaac to be raised by his mother alone beginning at age four. Following in his father's footsteps, the young Isaac showed a knack for, and sought education in, mechanical and electrical engineering, a field in which he soon excelled. Isaac was selected for admittance by a prominent and exclusive engineering school, but could not afford tuition; it is implied that the reason for this was his mother's association with the Church of Unitology.
Isaac attended a less prestigious school largely via financial aid and scholarship, and enlisted in the Merchant Marines soon after graduating with honors. He was quickly promoted within the organization for his resourcefulness. Isaac is currently trying to locate his father, a pursuit which has been obfuscated by the complete classification of his father's service records. It is indicated that at some point prior to the incident aboard the USG Ishimura he had been living with a medical officer named Nicole Brennan.
His name is a mixture of renowned Science Fiction authors, Arthur C. Clarke and Isaac Asimov.
During the events of Dead Space, Isaac is a crew member on the small repair vessel, the USG Kellion, deployed to find out why the mining ship USG Ishimura has gone dark, only to discover that the ship has been overrun by dead bodies mutated by an alien virus into the murderous abominations known as Necromorphs, which were somehow created by the influence of the Red Marker. To survive, Isaac travels through the Ishimura, repairing some of the extensive damage to the ship and constantly fighting for his life against the bloodthirsty Necromorphs. All the while, he is motivated by the prospect of rescuing his former girlfriend, Nicole, who was stationed on the Ishimura before it was breached.
After Isaac retrieves a singularity core from the severely damaged military vessel USM Valor, which was similarly infested by Necromorphs, he meets a surviving scientist, the lapsed Unitologist Dr. Terrence Kyne. Together, they plan to return the Marker to its rightful place on the surface of the planet Aegis VII, which has been totally overtaken by Necromorphs. Before they can leave the Ishimura, however, Isaac is betrayed by his fellow crewmate Kendra Daniels, who had stowed aboard the Executive shuttle and killed Dr. Kyne with a divet pistol.
Kendra leaves in the shuttle, but Isaac remotely orders its return. Before it docks in the Ishimura, however, Kendra exits via escape pod en route to Aegis VII. Isaac pilots the shuttle to Aegis VII, along with the Marker and Nicole. He returns the Marker to its pedestal, where it is amplified to subdue the power of the Necromorph Hive Mind and destroy all of the smaller forms that had been plaguing Isaac - as well as causing Nicole to disappear. The signal from the Marker disrupts the geo-orbital tethers holding a giant chunk of the planet in place, triggering an alert that informs Isaac of the imminent impact. Shortly after, Kendra Daniels traps Isaac, and shows him the final portion of a video recorded by Nicole Brennan that had inspired Isaac to investigate the Ishimura in the first place. The part of the video he'd never seen before revealed the terrifying truth: prior to the Necromorph invasion, Nicole used an empty hypodermic needle to induce an air embolism in her heart, and committed suicide, rather than die in agony at the misshapen hands of the Necromorphs. Nicole had been dead long before he arrived, and he'd been hallucinating her messages and physical presence the entire time.
Isaac is startled by the revelation, but regains his composure and pursues Kendra, who left the area with the Marker. Before he could reach the shuttle, he is blown over by the roar of the colossal Hive Mind. With a few swift thrashes of its tentacles, it brutally kills Kendra. After Isaac destroys the conspicuous yellow pustules on the Hive Mind's face and inside its mouth, the mammoth beast collapses into the crater it was once contained within. Then, Isaac quickly runs to the shuttle, takes the controls, and flees the planet, just as the chunk of ore crashes into its surface and destroys the colony, as well as the Hive Mind and the Red Marker.
As Isaac floats through space on the executive shuttle, reflecting on his daunting adventure, he watches the video of Nicole yet again, something he'd done throughout the story. This time, though, he stops the video himself, indicating that he is letting go of Nicole - just before a Necromorph made from Nicole's body attacks Isaac. Then, the credits roll.
Dead Space 2
Set three years after the end of the first game, Isaac awakes in a mental hospital with no memory since escaping the Ishimura. He finds himself on the Sprawl, a space station located on Saturn's moon Titan, which has been infested by the Necromorphs. Disoriented and suffering from dementia, he follows the intrusions of others to help him survive. Equipping himself with new RIGs and weapons, Isaac seeks to put an end to this outbreak, even as haunting visions of his dead girlfriend, Nicole, stalk him through the dark corridors of the Sprawl. Along the way to destroy the new Marker he believes is the root cause of the outbreak, Isaac must battle the reanimated corpses it has transformed, the crazed Unitologists who worship it, and the government who wish to use its mysterious power.
In this sequel, Isaac is no longer a silent protagonist, speaking naturally, and his face is seen much more frequently, in sharp contrast to the original which features no voice acting for the character and is only seen out of his helmet at the very beginning and ending of the game.
Dead Space 3
Two years after the events of Dead Space 2 and the destruction of Titan Station, Isaac and his new partner, an EarthGov soldier named John Carver, head to the arctic planet Tau Volantis, in search of Ellie Langford, a supporting character from Dead Space 2 and Isaac's now ex-girlfriend, who believes they'll be able to uncover a method on the planet once used to put an end to a Necromorph outbreak, hoping to use this secret weapon to put an end to the Markers and their horrible creations once and for all. However, their ship crash-lands on Tau Volantis, which is suffering a Necromorph infestation of its own, leaving Isaac and John stranded. Making matters worse, it quickly becomes clear that both of them are mentally unstable, being affected by the power of the Markers that litter the planet. Isaac and John must work together to survive the endless Necromorph assaults, as well as the murderous Unitologists who worship the monsters and litter the colony, hunting our heroes with heavy weaponry.
Isaac also cameod in a handful of games made by Electronic Arts after his wildly successful debut, appearing as a playable golfer in Tiger Woods PGA Tour '10, a skateboarder in Skate 3, has his armour available as an unlockable code for Dragon Age 2 via a Dead Space 2 preorder bonus, and even battles his way into Hell itself as an alternate skin in Dante's Inferno. He also makes it rain threes in NBA Jam: On Fire Edition. To date, Isaac has appeared in three actual games and cameoed in six. Also, two versions of Isaac's armor appear as outfits for Battlefield Heroes as paid content.