I thought this was going to be for the shitty American remake sequel, but it's for the Spanish one, so I calmed down.
It takes place 15 minutes after the ending of the first movie and follows the other side of the plastic sheet draped over the building. The first movie (the original...NOT the one where Jennifer Carpenter huffed and puffed throughout the whole movie) was incredibly good and scary. I don't know if it a sequel is warranted but I'll take it. It looks pretty scary.