At the same time, Caine is made aware - via his girlfriend, coroner Diane Pallone - of a series of drug-related deaths. The corpses are full of heroin, but the cause of death is a puncture wound to the forehead. Unknown to Caine and the police officers, the deaths are caused by an alien who is extracting something from the victims, but is being pursued by Azeck, a similar alien to himself.
https://en.wikipedia.org/wiki/I_Come_in_Peace