'Pretty Little Liars' Season 5 Spoilers: 100th Episode Marked the Return of A

Tuesday's episode of "Pretty Little Liars" not only marked the 100^th episode of the series, but also featured the return of several familiar characters such as Jenna, Caleb, and of course "A," who was initially thought to be dead.

"A" marked his return by blowing up Toby's house, and he appears to be equally pissed off that Alison is back in town.

Tuesday's episode featured Alison's first day back in Rosewood High, and things do not go exactly as she planned. Alison's former foes are not ready to let go of the past, and Mona and her army are out for revenge.

Mona succeeded in exposing Alison's true colors when she managed to secretly capture a video of Alison slapping her, and revealing what she really felt about everyone at school. And if spoilers for the upcoming episode are any indication, life is going to get even more complicated for Alison, as she gets entangled in her own lies.

Nothing has been going Alison's way since her return to Rosewood, and she contemplates leaving the town for good. However, the Liars – Aria, Emily, Hanna and Spencer – convince her to stay back in town so as to help them figure out who is behind the bomb blast.

Ezra, who is now officially back with Aria, will also be a part of the Liars' gang as they investigate the blast.

Meanwhile, Caleb, too will be second-guessing his return, and viewers will get to see him go down a very destructive path in the upcoming episodes.

"He's just openly questioning life as a whole," Tyler Blackburn, who plays Caleb, told HollywoodLife. "I think that he doesn't trust the world anymore and when that happens, you really start going down a dark path."

"He shuts off and I think that's actually part of the reason why he isolates himself so much — he feels like he's crazy and he's in it alone."

But he won't be alone for long, as some of his friends will lend him a helping hand to deal with his self destructive behaviour and self medication problems.

"Toby (Keegan Allen) kinda steps in [and] even Spencer (Troian Bellisario)," Tyler revealed. "They start to see what he's dealing with and it's not pretty so he has a little bit of a support system but it also pushes them away a lot.

"She's the one who's dealt with her own demons and her own self medication, and Toby's just sort of a pretty level-headed guy, pretty calm...plus, Caleb and Toby have a little bit of a bromance," Blackburn added.

"Pretty Little Liars" episode 6 is titled "Run, Ali, Run" and it will air on July 15, 2014.