”Walking Dead” returns. (AMC). | GALLERY: Click the image for more pictures from season two.

“The Walking Dead” returns to AMC on Sunday with more episodes focused on the zombie-pocalypse struggles of Sheriff’s Deputy Rick Grimes and his fellow remaining non-flesh-hungry survivors.

Washington Post TV critic Hank Stuever says in his review of Season 2 that the upcoming episodes are sleeker and more frightening than what we saw during Season 1. But wait ... what was it we saw during Season 1 again?

Ten months have passed since the airing of the “Walking Dead” Season 1 finale — you know, the one in which the Centers for Disease Control exploded. Understandably, some fans may need a quick refresher before they jump back into the world of Grimes, guts and gunshots fired at the foreheads of the undead.

Here are five plot points from last season to keep in mind as we embark on Season 2, which will be recapped starting Monday here in Celebritology. Need more detailed memory refreshment? Past episodes of “Walking Dead” can be viewed on Netflix or On Demand. And, of course, feel free to visit Celebritology’s previous recaps from Season 1.

1. Rick Grimes (Andrew Lincoln) still doesn’t know about the affair between his best friend, Shane, (Jon Bernthal) and his wife, Lori (Sarah Wayne Callies).

The sheriff’s deputy was in a coma for awhile during the rise of the walkers, during which time Shane protected Lori and became her lover. After miraculously waking up from said coma during Season 1, Grimes even more miraculously managed to track down his wife and son Carl (Chandler Riggs). But neither Lori nor Shane has shared their big secret with him.

2. Shane still wants to be with Lori.

He made it clear that he still has strong feelings for her in the Season 1 finale, but she rebuffed his advances — the kind of rebuffing that leaves scratches on a person’s neck. Season 2 teasers suggest Shane may try to break off from the core group and battle the walkers solo to put some distance between himself and the Grimes family.

3. Andrea remains suicidal.

After the death of her sister — you know, the one she got that mermaid necklace for in Episode 3 of Season 1 — Andrea (Laurie Holden) lost the will to live and was hoping to end her life at the CDC. But Dale (Jeffrey DeMunn) saved her. So she still has a death wish, and a grudge against Dale.

4. What did Dr. Jenner tell Rick Grimes?

At the end of last season’s finale, as everyone fled the CDC building, Dr. Jenner (Noah Emmerich) whispered something in Grimes’s ear. What was that something? We are supposed to find out in Season 2.

5. Merle remains missing.

Remember that oh-so-charming racist guy that the survivors chained to a rooftop and left for dead? He managed to escape, but we don’t know his whereabouts. Is it possible that, as some fans have suggested, he could wind up being The Governor, who is known to readers of the “Walking Dead” comics?