I'm trying to locate a YA remix of the the body-snatcher/puppet-master theme that gave me nightmares when I read it in Danish some time in the mid-1980s:
Earth is being invaded by parasitic mind-controlling aliens. The aliens are on the run from the destruction of their home world, and there may be a prologue telling from their side how one of their scientists invented a method for beaming their personalities to hosts on a foreign world (that is, Earth).
The First Victim is a scientist who is was examining a recently discovered mummified alien head. They know it's alien because it has only a single broad incisor in the center of the jaw, rather than the paired ones we ordinary folk have. The scientist neglects to take safety precautions before cutting open the head, and discovers too late that it contains live microorganisms.
Once infected, First Victim takes to growing blob-like alien brains in vats. One of the early victims is a guest in his lab who is skeptic about the project. First Victim says something like "but it's alive and it's intelligent". He grabs a blob out of the vat and throws it at the guest's face, and it seeps through the skin and infects the guest.
Near the end of the story (?), authorities are preparing to stop the invasion by nuking the infected town. As a last-ditch attempt at a peaceful solution they send one or more of First Victim's immediate family in to negotiate "as they have shown a certain immunity to infection" -- apparently he kept some part of his human mind and was able to resist infecting his loved ones.