Spoilers ahead for Season 2 of 13 Reasons Why.

The first season of 13 Reasons Why was driven by Hannah's cassette tapes, a sort of audio diary she left behind to chronicle the events leading up to her suicide. But while her side of the story had ended by the time the show reached its finale, the rest of the school's hadn't, and Season 2 expands to probe the perspectives viewers had yet to see.

It also introduces a new mystery. As Hannah's parents press forward with their case against Liberty High, an unknown sender begins leaving polaroids for Clay, eventually leading him to another dark secret hiding within the halls of Liberty. Behind the baseball field is a hideout dubbed the "Clubhouse" where Bryce and other skeevy players have apparently been taking girls to get them drunk and assault them, showing that Hannah and Jessica were just two in a long line of Bryce's victims.

The photos launch Clay on a crusade to expose Bryce and take him down in court, but the identity of the sender remains a secret for the bulk of the season. So for all of those too eager to know to get through its 13 episodes, who's behind the polaroids?

In Episode 10, "Smile Bitches," Clay and Justin finally break into the clubhouse in search of more proof, only to be interrupted by Zach. He warns them that the more they dig, the more retaliation they'll face: Bryce and his minions will stop at nothing to keep them silent. Clay insists he's not afraid, and Zach says, "good," then leads them to the box with the rest of the photos, revealing himself as the sender.

When Clay asks, incredulous, why he didn't just come talk to him, Zach retorts, "Because I'm a f--king coward, and you're not," then storms out.

So, essentially, Zach didn't have the courage to say something about the clubhouse, but thought Clay did — and he was right. Backed by Justin and Jessica, Clay tries to get the photos evaluated in court, and it works, partially: Someone steals the pictures before he's able to submit them, but the situation helps give Jessica the strength to take Bryce to trial.

He only winds up with probation, but it's enough to make him lose his scholarships, transfer schools, and, ostensibly, get a mark on his legal records. It's a small victory, but more importantly, one that allows Jessica to begin to heal.

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