Sheriff Brackett learns his daughter Annie was killed by Michael, and angrily blames Loomis for letting him escape and leaves the search to Deputy Gary Hunt.

As Loomis investigates he discovers clues connecting Michael to the occult practice of Samhain, suggesting an explanation to his seeming invulnerability and murderous desire.

Wynn reveals that Jamie's baby represents a new cycle of Michael's evil that he kept secret from most of the cult who were focused on inflicting the curse onto a new child, Danny.

They succeed, and after regaining consciousness, Loomis helps them escape the hospital while Tommy subdues Michael by injecting him with large quantities of tranquilizers.

Back inside the building, as seen in the theatrical version, Michael's mask is shown lying on the floor of the lab room, and Loomis is heard screaming in the background, leaving the fate of both men unknown.

In the original “Producer’s Cut” of the film, after telling the others he has got "a little business to attend to", Loomis walks back into the sanitarium to find a seemingly-defeated Michael lying on the floor of the main hallway, after being stopped by Tommy, who used runes.

Loomis comes to believe that Michael has returned to find his little sister, Laurie, who Brackett helped get adopted by the Strodes after her mother committed suicide.

"[20] Doug Bradley observes that Dr. Loomis "spends a lot of the film warning people they don’t know what they are dealing with" and this provides Michael with "this supernatural, mysterious element that made him so powerful.

"[21] Dustin Putman views Pleasence as having brought "authority, dignity, and vulnerability" to the Loomis role and defines the character as "a man who once cared for Michael, who can't help but feel as if he still shares a bond with him, but who has grown wearisome because he now knows that there is no way of getting through to him.

"[25] In Halloween 2, Geoff Cox asserts, viewers "witness Loomis grow increasingly more exasperated that Michael’s still on the loose, confused about how he took bullets to the chest and walked away but vindicated in his belief that Myers is less a man and more a force of pure evil.

"[26] Devon Elson observes that the early demise of a Michael lookalike "mechanically serves as a narrative reset to have the police disbelieve Loomis again.

"[32] Jack Wilhelmi viewed the inclusion of the Jamie Lloyd character as giving both Loomis and Michael "a tremendous amount of depth and characterization" and "a foil to build off of and play against.

"[35] James Berardinelli called Pleasence "the stabilizing influence" in his review of Halloween 4 and observed that "the character of Dr. Sam Loomis, even as beaten and broken as he is in the later installments, represents a rock of solidity.

Anderson explains that Loomis views himself as the only one who can stop Michael and "knowing that he may not have much time left on this Earth, his growing obsession with ending Myers at any cost is a believable progression in a character who has dedicated the second half of his life to containing and obliterating the evil that lives within Michael—even if it means putting Jamie squarely in harm’s way.

"[39] Berardinelli theorizes that "one could construct an argument that the good doctor’s obsession, combined with the various physical and mental experiences he has gone through, might have taken him off the deep end" and that Loomis could be argued as having become just as deranged as Michael.

"[41] Culture Crypt notes that Loomis "never even confronts Michael Myers one single time in Halloween 6, often doing his own thing on a parallel arc to what Tommy Doyle and the Strodes do on the main one.

[45] Due to both being doctors who serve as the archenemy to a supernatural antagonist, a number of commentators have compared Loomis to Dracula foe Abraham Van Helsing; the list includes Kyron Lewis,[46] Christian Bone,[47] Tony Fyler,[48] Cody Hamman,[49] and Padraig Cotter.

[53] Producer Irwin Yablans then suggested Pleasence, who agreed to star because his daughter Lucy, a guitarist, had enjoyed Assault on Precinct 13 for Carpenter's score.

[56] While filming the final scene of the movie, where Michael is revealed to have disappeared after being shot by Loomis and falling off a balcony, Pleasence asked Carpenter if he should do an expression of surprise or an "I knew it'?"

[58] After the 1982 release of Halloween III: Season of the Witch, the lowest performing film in the series at the time,[59] executive producer Moustapha Akkad wanted to make a sequel that brought back Michael Myers.

In 1998's Halloween H20, the voice of Dr. Loomis is heard giving the same speech that he gave to Sheriff Brackett when they were inside Michael's abandoned childhood home in the original film.

[69][70] For Halloween Kills, Loomis was physically portrayed by the film's construction foreman Tom Jones Jr., whose resemblance to Pleasance was enhanced with prosthetic makeup; Mahan again provided the voice via dubbing.

[74] Screen Rant listed Loomis as the second best Halloween character (behind Michael Myers), asserting that "Pleasance truly gives one of the best performances in Horror films as the determined doctor.

"[81] Berardinelli referred to Pleasence as the "saving grace of Halloween II" and that the film "belongs to Loomis, the gun-toting action figure who arrives in the nick of time and has more good one-liners than everyone else put together.

"[85] While admitting that Loomis was "the most interesting" character in Halloween 4, Edison Smith viewed him as suffering the most from the film's repetition of the Myers storyline, with Pleasence's "once-iconic turn beginning to smack of self-parody" whose only growth was "becoming a John McClane style action hero who crashes through windows and leaps fifty feet through the air to avoid gas station explosions".

[86] The character's portrayal in Halloween 5 has also received negative reception,[87][88] with Richard Harrington of the Los Angeles Times rebuking Pleasence for giving "a flat two-note performance".

"[93] Eric Hatch[94] and Berardinelli, both of whom disliked the sixth film, bemoaned that it was Pleasence's last appearance in the series,[95] with Sparks asserting that "Pleasance deserved better, especially at the end of his career.

[97] NECA produced a two-pack of 7-inch figures of Loomis and Michael from Halloween II to celebrate the film's fortieth anniversary the following year.

[101] The fifth film in the Scream series stars Melissa Barrera as Sam Carpenter, who is revealed to be Billy's daughter, with her technical name being a nod to the Halloween character.

[103] In the 2002 film Blood Feast 2: All U Can Eat, John McConnell and Mark McLachlan play detectives Dave Loomis and Mike Myers, named after the Halloween characters.