The city 17 is still in battle against the combine and the city is evacuated by the Citadel destroy, Gordon Freeman does not know if there are any dark places in the city like for example the tunnel, find the exit of the light to evacuate the city 17.
In the content there is a folder SDK Base 2013 If you had no Half-Life 2: Episode Two and the folder Dark 17 is for HL2EP2
some install instructions would be very helpful thanks