Halloween III: Season of the Witch (1982) on Netflix

Daniel Challis, a doctor in a northern California hospital, treats a scared old man named Harry Grimbridge who screams "They are going to kill us!" while clutching a Halloween mask from the number-one best-selling Silver Shamrock mask company. But later Daniel is shocked when later that night Harry is murdered in his hospital bed and the killer walks calmly to a car and blows himself up. His curiosity is piqued when Harry's daughter Ellie arrives and tells Daniel that Harry was scared ever since he tried looking into the origins of the masks, since no orders for them are being taken for the following year. Daniel and Ellie go to Santa Mira, the home of Silver Shamrock, to uncover what happened and are horrified to find out that the owner of the mask company, Conal Cochran, is planning to use the masks and some black magic as one great Halloween trick on the children who are wearing his masks that coming Halloween. As time draws near on Halloween night, Daniel must stop Cochran from sending the signal out to activate the masks, and he can only do that if he can get out of Cochran's huge mask factory alive....