Nothing succeeds like success. After the low-budget Halloween became a surprise hit, a sequel was all but inevitable. Halloween II made some wise choices, keeping things simple and direct.
After surviving her attack by Michael Myers, Laurie Strode (Jamie Lee Curtis) is rushed to the hospital. Over her objections, she is sedated, where she dreams of her past, including her adoption. Meanwhile, Dr. Sam Loomis (Donald Pleasance) and Sheriff Brackett (Charles Cyphers) are in a mad pursuit of Michael, who is not only stubbornly alive but killing his way around town. Once he hears where Laurie is, it's off to the hospital to kill Laurie once and for all.
EMT Jimmy (Lance Guest) has taken a shine to Laurie, but Head Nurse Ms. Alves (Gloria Gifford) will have no hanky-panky in her ward. If only Ms. Alves knew what was going on at Haddonfield General. Smarmy EMT Budd (Leo Rossi) and Nurse Karen (Pamela Susan Shoop) have been in a love/hate torrid affair. Despite the danger, Budd and Karen have a tryst in the therapy pool, where Michael finds them.
Michael is on a full-on killing spree to get to Laurie, but why is he so fixated on her? As Loomis is forcibly escorted out of Haddonfield by Governor's orders, he learns a shocking secret: Laurie is Michael's long-lost sister. Realizing Michael will not stop until he kills her, Loomis forces the Deputy to bring them back to the hospital. The body count is already high, but will Laurie and Loomis both survive Michael Myers' fatal wrath?
Halloween II works because it kept to the formula of the original Halloween. Cowriters John Carpenter and Debra Hill opted to start right from where Halloween ended, which kept the story flowing. While we had Loomis and Laurie separated for most of the film, their stories did not seem to interrupt the other.
I would argue that this is because we spend most of the time at the hospital. Fortunately, when we were not with Laurie, the Loomis story worked well. It also gave viewers some of Halloween II's more shocking moments. Of particular note is when the semi-crazed Loomis chases someone he thinks is Myers. The resulting fiery crash is jolting in its "just-graphic-enough" manner. That one suspects it might not be Myers (and I think most Halloween II viewers would have thought it was not) makes it more shocking. Audiences have knowledge the characters don't, so they realize the real horror of this particular incident.
Halloween II has more kills than Halloween. At nine (by my count), it is almost double that of the first. Surprisingly, despite the eventual franchise's reputation for being gory, I don't think Halloween or Halloween II were excessively graphic. Some deaths were even off-screen. Some also did not involve knives.
Budd and Karen's end were quite clever and well-crafted, a credit to director Rick Rosenthal (Carpenter not directing the sequel). Again, the audience is put ahead of the characters, which builds up the tension. Karen's death is not unexpected but not as graphic as it could have been.
Her and Budd's demise does, however, give new meaning to "turning up the heat".
The performances are also quite effective. Curtis is not as active here as she was before, but in her blend of vulnerability and strength she develops the Laurie Strode character. Pleasance veers close to crazed as Loomis, forever convinced that Michael Myers is some kind of almost superhuman evil.
The smaller roles are also well-acted. Guest's Tommy has a sweetness to him, balanced by Rossi's pervy Budd. Gifford does not go full Nurse Ratchet as Ms. Alves, but she makes clear that she is not to be trifled with. Shoop makes Karen not into a bimbo but a basically decent person who is also a bit randy.
Some elements in Halloween II might not quite work together. I don't think we learned if Tommy lived or died. I also think the connection between Michael Myers and the Celtic mythic figure Samhain: The Lord of the Dead quite worked how I think the film intended. Other deaths seem to be almost irrelevant to the overall story.
Those ultimately are minor points. Halloween II is a strong and more importantly logical sequel to the original. It also manages to work on its own, though I figure people would not see Halloween II cold. On the whole, Halloween II is a competent and well-shaped film and sequel.