The Employee: Official Collections is exactly what it sounds like. The official collection pack for the Employee series. More maps will be added when they are released.

Complete storyline (hover mouse over spoilertext to read) spoilers are broken.
Map 1: You are one of the robotic employees working at Aperture Science Laboratories. The labs are monitored by the adminestration bots GLaDOS and Wheatley. Your job is to run routine maintenence check for the nuclear generator located in the facility. However, this morning, everyhting vent wrong. The reactor started a chainreaction, and the facility starts to self-destrcut...
Map 2: Waking up in a ruined reactor chamber, you must escape the facility. On your way out, you witness the destruction cuased by the meltdown. As you are a robot, you have survived all the radiation and destruction. There are fire everywhere, and your path is blocked. Nothing your trusty old portalgun can't fix...
Map 3: After finding a broken diversity vent, you were taken far through the facility. Eventually, you ended up in a semi-broken test chamber. Solving it using your portalgun, you made it through. There, you met one of the many Aperture Science Personality Constructs, a core named "Rick", he takes you to an abandoned office area. Suddenly, the lights turns off. However, as stated before, you are a robot, and robots have a built in nightvision feature. Later on, you reach the rocket tests lab, and for some reason, you knew the code for the door. Making it to the surface, you find out that the comunications network is offline. You will have to launch the rocket in order to get a satelite into orbit. There is just three small problems: No power, fuel or oxygen. You set off to find the Aperture Science Powerplant to restore the power...