'The Walking Dead' season 8 premiere brings all-out war

— -- Warning - spoilers ahead.

The season eight premiere -- and 100th episode -- of "The Walking Dead" begins with Rick Grimes apparently daydreaming in the heat. He pictures flowers in a peaceful room. In reality, he's at Hilltop, staring at a grave while preparations are being made to harden vehicles.

At Negan's Sanctuary, Dwight is sitting on his own when a crossbow bolt pierces a motorcycle tire. He plucks it, and there's a note attached: "Tomorrow," it reads. On an overpass, Tara and Carol make note of the time and wait. Something big is coming.

Rick addresses his united group of Alexandrians, Hilltop residents and Kingdom subjects, riling them up about their right to take back what's theirs. He vows that whoever tries to stop him will meet their end, though there's only one person who has to die: Negan.

At the Sanctuary, Dwight writes a note, attaches it to an arrow and fires it back. We see Daryl fetch it and read the very old-school instant message.

Tara and Carol, meanwhile, watch the walker horde shuffle below them.

Rick, his eyes lined with red, again pictures that flower-filled room ... and himself in a bed, his face overgrown with a long grey beard.

After the opening credits, we see Carl driving before stopping to try to scavenge some gas. He hears a noise and draws on a series of voices to find one guy talking to himself. A gunshot rings out, and the man scrambles. Cut to a checklist, and somebody literally crossing off sentries from a kill list as each is dispatched. It's Daryl, taking no prisoners. Neither is normally Zenned-out Morgan. He runs a guard through the back with his staff.

Back at Alexandria, Rick looks nervous. He gives little Judith a kiss on the head, kisses Michonne, and hugs Carl. Leaving them behind, he and the others drive off in vehicles with metal plates welded to one side.

Rick gives the all-clear and the convoy advances. Rick's gang assembles, with their retrofitted cars, in an empty field. He talks to Maggie, who thanks him for his leadership. He notes, "After this, I'll be following you."

On the overpass, Morgan, Carol, Tara and Daryl split up, and their first trap kicks off: an SUV explodes.

At the Sanctuary, residents hear the explosion and scramble their security forces.

Dwight takes a smoke break just as another guard falls, and Rick's gang assembles behind their maze of fortified cars, penetrating the undefended Sanctuary. His men fire in the air, hoping to draw out Negan's men. They wait, until Negan himself comes out, smiling as always, surrounded by his lieutenants.

"I'm sorry," Negan says, "I was in a meeting." He tells Rick he knows he's currently outmatched, and he won't sacrifice his own people. Rick offers for Negan and his leadership to surrender, and only he'd pay the price.

"You think you have the numbers for this fight?" Negan asks. "You don't."

He then reveals that Gregory, the head of Hilltop, declares his allegiance to Negan, and demands any Hilltop people surrender and return to their homes.

None break rank, to Gregory's surprise.

Angry at all he "invested" in Gregory, Simon casts the coward down a flight of stairs. Elsewhere, Negan's patrol hits booby traps, their cars exploding.

Rick again tells Negan's people to surrender. He counts down, before opening fire at "seven."

Rick's gang wastes a tremendous amount of ammo firing at windows before moving their fortified cars to better positions, while Daryl's gang breaks up into groups, with him hopping on a bike to lead the horde toward the Sanctuary.

At Sanctuary, Rick uses the RV as a car bomb, blowing through Sanctuary's outer defenses. An injured Negan hobbles out from the main building. Rick fires in vain; although he's pinned down, Fr. Gabriel urges him to flee. Rick snaps a Polaroid of the pinned-down Negan and leaves.

Fr. Gabriel spots Gregory the coward, and stops his truck to help him. For his efforts, Gregory steals his truck and leaves the priest to die. Rick regroups with Daryl and tells him he had to let Negan go.

Elsewhere, Carol and a contingent of Kingdom subjects strike Negan's satellite outpost -- as the horde descends on Negan's Sanctuary. Scrambling, Fr. Gabriel looks for somewhere to hide, and ends up in the same trailer as Negan himself. "I hope you got your s------ pants on," he tells him. "Because you are about to s--- your pants."

The camera pans up to show the entire horde descending on the trailer.

The episode ends where it began, with Old Rick dreaming of a life beyond this: Judith as a little girl, and peace at Alexandria and presumably elsewhere.

The episode also includes a coda memorializing John Bernecker, the stuntman who was killed filming this season of the show, as well as the late director George Romero, whose "Night of the Living Dead" spawned the zombie genre.

"The Walking Dead" returns Sunday at 9 p.m. ET on AMC.