Isaac Clark is the main character of the game's Dead Space & Dead Space 2. His name is a combination of Isaac Isimov and Arthur C Clarke.
-Summary of Dead Space-
Isaac Clarke is an engineer who is sent on a mission to the USG Ishimura, a mining ship orbiting a planet named Aegis VII. While investigating the disaster that has befallen the ship, he is also trying to determine the whereabouts of his girlfriend Nicole, a doctor upon the ship. As the game progress's, Isaac discovers a conspiracy involving a religious cult named "The Church of Unitology" and the Government.
-Summary of Dead Space 2-
After waking from a coma on a massive space city known as "The Sprawl," the lone survivor of a horrific alien infestation finds himself confronting a catastrophic new nightmare. Battling dementia, hunted by the government and haunted by visions of his dead girlfriend, Isaac will do whatever it takes to save himself and rid the city of the gruesome, relentless Necromorphs.