C++ Programmer Source Engine job - Zeta Squad mod for Half-Life 2

After the Combine take over, a portal storm in city 15 sets off the nuclear reactor into total meltdown.While causing a Level 7 incident the combine did not leave. City 15 functioned as normal under combine rule, until a year later were significant reports by the civil protection members noting the high radiation level,large drops in population,and unknown creatures. That's were you come in, you are a part of Zeta Squad a group of 4 combine in for clean up and recon. but you discover more then just head crabs on your venture