RES addon - Half-Life

You are Gordon Freeman, it's been a while since the little problem at Black Mesa.Somehow you escaped and have been hiding for a while, everything has been pretty quiet up untiltoday. Early in the day you got a radio message from a research facility code named 'RES' whichhas received some of Black Mesa's creatures after the accident. The scientist gave you thelocation of the back entrance to the facility which is where you are headed now. While you'redriving there, he explains how the aliens took over the research labs, but since RES'scontainment system is better, it managed to contain the aliens in the research labs...unfortunatly the scientists are stuck down there too and now the military are entering the baseto kill everything and everyone related to the accident. He also tells you about how some of thesecurity force has gone berserk and are also killing scientists.
Finally, you have arrived in the desert canyon it's late, but the scientists need you, sothat's just how it's gonna have to be. You repel down into a cliff, unfortunatly, your ropebreaks and you fall down. No damage was done, but you have left all of your stuff that youbrought with you on the top of the canyon. You turn around and see a security guard... dead. Hemust have tried to escape... You grab his equipment and get ready to figh