|“||The third channel, it's still on. Please, take off the third channel. The third channel, it's still running. Stop it, please, for God's sake, please stop it. There's no more time! Please stop it. Stop it now. Turn it off! Stop it! Stop it! Stop it! Stop it! STOP IT!||„|
|~ Dan Challis' famous quote at the end of the film.|
Daniel Challis is a hardworking doctor who at some time in his life met and married his ex wife named Linda Challis. They had two children named Bella Challis and Willie Challis. At some point Daniel started to became very busy with his work, which possibly started him on his road to becoming an alcoholic. Linda had enough of the problems she was having with her husband and they got a divorce, with Linda keeping custody of the children.
On October 23, a man named Harry Grimbridge is brought into the hospital where Challis works trembling with fear and clutching a popular Halloween mask. Grimbridge is killed that night in his sleep by an unidentified man who blows himself up in a car. Challis is confronted the next day in a bar by Harry Grimbridge's daughter, Ellie. He tells her about the strange events of the previous night and shows her the very mask he was holding.
Working with Ellie, Dr. Challis traces the mask back to Silver Shamrock Novelties in Santa Mira. While in Santa Mira, Ellie mysteriously disappears and Challis is captured by Cochran's androids while on the run. Challis discovers Cochran's plan to kill millions of children on Halloween night using his masks. He finds out that the Silver Shamrock trademarks on every mask contain a computer chip and a small fragment of Stonehenge. On Halloween night, a commercial would air activating the computer chip, causing the mask wearer's head to dissolve and erupt with insects and snakes. Cochran shows this to Challis in a demonstration in which he kills the Kupfer family.
Challis escapes captivity in Cochran's factory and rescues someone he believes to be Ellie. He destroys Cochran and the factory by dumping the Silver Shamrock trademarks everywhere and airing the commercial that activates the computer chips inside. However, when Challis is returning home, he is attacked by the android that he thought was Ellie. He escapes the android after a grueling battle and runs to a nearby gas station, where he tries to convince the station managers not to air the Silver Shamrock commercial. He persuades them to take it off channels one and two, but not the third. Challis is last seen yelling, "Turn it off! Stop it! Stop it!"