Sony PicturesWarning! Spoilers ahead for 28 Years Later.To Danny Boyle, the 28 Days Later films have always been about family: the scrappy found family of Jim (Cillian Murphy), Selena (Naomie Harris) and Hannah (Megan Burns) in the first film; the troubled family at the center of 28 Weeks Later; and now, Spike (Alfie Williams) with his ailing mother (Jodie Comer) and brash father (Aaron Taylor-Johnson) in 28 Years Later.“I think it's fundamental clearly to these films: At the core, these are family dramas really, and it's built out of that,” Boyle tells Inverse.But 28 Years Later has a few more things going for it than the “intense family drama plays out between a mother, father and the son,” Boyle says. There’s the new “family” of an Infected-hunting cult that gets introduced in the final minutes of the film. And, of course, there’s the “family” within the Infected: the Alpha and the Infected woman who he’s impregnated. It’s a shocking new twist in the lore of the Infected, who have evolved beyond the corpses that fell to starvation in 28 Weeks Later. Boyle breaks down the evolution of the Rage Virus, how the ending teases the new trilogy, and when we’ll finally get to see Cillian Murphy’s Jim onscreen again.The Alpha InfectedJamie and Spike running from the Alpha. | Sony PicturesIn 28 Years Later, the British mainland has been quarantined for nearly three decades since the Rage Virus first broke out, with the hope that the Infected would eventually wither away from starvation. But as the remaining humans have spread out and learned to survive, forming their own little communities like the one that Spike, Jamie, and Isla are part of, so too have the Infected.“What's happened in that 28 years is the survivors have evolved,” Boyle says. “But it's also how the virus itself has survived.”The Infected have learned to drink, they’ve learned to hunt, and they’ve learned to live in packs. We see this in the scenes of the pack led by the Alpha which attack Jamie and Spike during Spike’s first hunt on the mainland: The Alpha hunts a deer, tearing off its head and pinning it on a tree branch in a sort of ritualistic feeding — something that Boyle compares to how “dogs organize.” The Infected pack, led by an Alpha. | Sony Pictures“They won't be able to bring a deer down without that kind of pack mentality,” Boyle says. “And the pack mentality also throws up an Alpha, a dominant. And so that emerges as one of the evolutionary processes.”In the film, Spike reveals the prevailing theory for why Alphas began to emerge among the Infected: the virus acts as a sort of steroid on some people, enhancing their physical strength and intelligence until they appear to act with some kind of sentience beyond just rage. The virus has evolved in opposite ways too: the “slow-lows” are the slow, engorged Infected who live low to the ground and are generally more passive, “though still very dangerous if they're disturbed,” Boyle says.But the final ingredient, Boyle says, is “the pregnant infected that you meet towards the end of the film, and the baby that's born of that.”28 Years Later’s Ending, ExplainedRalph Fiennes’ Dr. Ian Kelson saves the Infected baby but after the Alpha tries to retrieve it, sends Spike away. | Sony PicturesAs Spike takes his ailing mother to Dr. Ian Kelson in hopes of curing her mysterious disease, Isla ventures into a rundown train, where she discovers a pregnant Infected in labor. Isla helps deliver the baby, to the horror of stranded Swedish NATO soldier Erik (Edvin Ryding), who insists on murdering the child to stop the Infected from breeding (an action that gets him immediately decapitated by the Alpha that fathered it). But Spike notices that the baby doesn’t seem to be infected, taking it to Dr. Ian Kelson. Kelson can’t save Isla, diagnosing her with cancer and offering to add her skull to his monument in order to save her from her final months of pain. But Kelson does help Spike save the baby, protecting it from the Alpha (Chi Lewis-Parry) — which Kelson nicknames “Samson” — and sending Spike off to bring it to safety.Spike ultimately leaves the baby with a kind family in his community, but refuses to return himself, betrayed by his father’s infidelity. He’s traveling on his own in the mainland when he’s chased by a group of Infected and runs into Jimmy (Jack O'Connell), a tracksuit-wearing cult leader whose gang members use parkour to take out the Infected. “[They] are some kind of weird, modernistic, track-suited family as well, a family gang, really with all their blonde hair,” Boyle teases of Jimmy’s cult. This cult will take on a more prominent part in the next film, 28 Years Later: The Bone Temple, directed by Nia DaCosta, Boyle says. “The second film continues that [family] theme and adds to it the nature of evil as well,” Boyle teases.So, Where is Cillian Murphy?Though Murphy is only an executive producer in 28 Years Later, Boyle confirms he’ll make an appearance at the end of The Bone Temple and play a major role in the third film. | Peter Mountain/Dna/20th Century Fox/Kobal/ShutterstockFans will have noticed that Cillian Murphy’s 28 Days Later protagonist does not appear in 28 Years Later. But Boyle teases that Jim will not only appear at the end of The Bone Temple, but he will play a major role in the third film.“You have to wait for Cillian, but all good things are worth waiting for,” Boyle tease. “And he's certainly a good thing. He was a producer on this film, 28 Years Later, and he begins to make an appearance in the second film. And then yes, our destiny is a full-on Cillian experience in the third film.”So, now that Spike is on a journey through the mainland, will that put him on a crash course towards Murphy’s Jim? “It'd be nice for Spike to meet up [with him],” Alfie Williams tells Inverse. “I mean, it's a small world, you never know!”28 Years Later is playing in theaters now.