Georgie’s right, once you open Pandora’s Box things will be changed forever. And, as the saying goes, it might seem like a small thing but it has far-reaching consequences.

In the case of Sunday’s new episode, “Pandora’s Box,” every small thing that happened on and off the ranch became bigger as the hour went on. And, I’m sure, will continue to loom larger as the season comes to a close. Lisa’s checkup turned into a medical scare that shadowed she and Jack until a follow-up phone call the next day relieved them both. But does Lisa’s pre-emptive plans to update her will hint at something sinister on the horizon?

Ty, who is seems has been gone from Heartland for weeks, was back and flip-flopping over whether to open the box his father had left for him. I knew he would eventually decide to take a peek inside and that cigar box held a flood of memories for Ty. His dad’s birth certificate confirming he lied about his age. A picture of Ty on the day he learned to ride a dirt bike. His mother’s engagement ring and a note explaining he’d scraped together enough money to buy it back after pawning it. Opening that plain paper wrapped parcel seemed small, but it held big significance for Ty: the man he’d painted as a criminal and scoundrel had tried to be a better person.

Georgie and Adam took a leap forward in their relationship. Yes, agreeing to “hang out” outside of studying appears to be minuscule, but it’ll change everything. Adam will be invited to those awkward family dinners that make me laugh out loud and Georgie will once again find herself under the gaze of Olivia, who I’m sure won’t be happy she lost Adam.

But perhaps the biggest box opened on Sunday was Lou, who took the plunge and made out with Mitch. The two have been bickering back and forth for weeks and I was silently thanking those guys for putting all of the dude ranch furniture on the roof because it forced Mitch and Lou to spend some time together. Once she realized he wasn’t a one-dimensional player, Lou dove in with both feet. After everything she’s been through, Lou deserves some happiness in the romance department. Of course, doing this opens up a can of worms. On the surface, how can they ever hope to keep their budding romance a secret from everyone? And in the larger scope, Lou’s decision affects Georgie and Katie, especially if she and Mitch get serious.

Speaking of serious, things get very serious next week when a suspicious-looking fire rages at the sanctuary, putting the animals and humans there in jeopardy.

Heartland airs Sundays at 7 p.m. on CBC.

Were you happy Lou and Mitch finally kissed? Think things will last between them? Comment below or on Twitter via @tv_eh.