At the end of Halloween 2 (1981), Dr. Loomis (Donald Pleasance) seemingly perishes in a fire alongside Michael Myers, only to return for Halloween 4. For the first half of the Halloween franchise, no character was more important than Loomis, outside of Michael himself. While Jamie Lee Curtis' Laurie Strode exited the series after two films, Pleasance's Loomis stuck around to play the Quint to Michael's Jaws for a further three sequels, right up until his death prior to the theatrical release of 1995's Halloween: The Curse of Michael Myers.
It could be argued that the longer Loomis fought Michael, the more unhinged he became, as seen in the way Loomis acts around Jamie Lloyd in Halloween 5. Yet, considering that every single thing Loomis says about Michael is true, it's kind of hard to blame him. Loomis witnesses this force of nature continue to claim victim after victim, despite the doctor's best efforts to stop him. The frustration and anguish involved in that pattern would be likely to drive just about anyone mad.
While Dr. Loomis emerged unscathed from the first Halloween film, the good doctor ended Halloween 2 in a much less healthy state, in that he appeared to be burned to a crisp. As fans would learn in Halloween 4 though, that wasn't actually the case.
Halloween 2: Dr. Loomis Sacrifices Himself to Defeat Michael
By the end of Halloween 2, Loomis has been stabbed in the gut by his former patient, but is still doing his best to protect Laurie. After Laurie Strode shoots Michael in the eyes, the two release gases into the Haddonfield Memorial Hospital's operating room, Laurie escapes, and Loomis intentionally causes an explosion designed to take out Michael once and for all. Sadly (or happily, for horror fans) that didn't happen.
Halloween 4: Dr. Loomis & Michael Myers Both Return
After Halloween 2, the franchise tried to go off in a new anthology direction with Halloween 3: Season of the Witch. While a cult classic now, the tale of the Silver Shamrock mask company wasn't popular when it released in 1982, and six years later, producers brought back both Michael and Loomis for Halloween 4. That film mostly glosses over the seemingly deadly explosion, leaving Michael in a coma since 1978, and having Loomis sport some unsightly burn scars in addition to walking with a limp.
Halloween 2: How Dr. Loomis Survived the Fire
While there isn't an explicit canonical explanation for his survival, the original Halloween 4 script written by Alan B. McElroy actually opened with a scene attempting to explain how Loomis survived. The scene was never shot, as director Dwight H. Little decided it would be better to not get bogged down in explanations. It would've seen the force of the explosion blow Loomis out into an adjacent hospital corridor, and away from the bulk of the fire. Sure, that explanation is a bit weak, but it's more than Halloween 4's theatrical cut offers. The more cynical reasoning is money. Halloween 3 tanked, and producer Moustapha Akkad really wanted to bring Michael and Loomis back. Halloween creator John Carpenter fully intended Halloween 2 to be the demise of both characters, but the only thing more powerful than Michael Myers is Hollywood's desire for cash.
