We really should have porn videos of females having sex for moneycome to expect it by now, shouldn't we? After the heartbreak of episode 3 and the agony of episode 5, everything was pointing to episode 7 of The Last of Usbeing another lesson in emotional torment.

And, sure enough, it didn't disappoint.

Ellie's (Bella Ramsey's) backstory about her childhood best friend and first love, Riley (Storm Reid), was a tragic gut punch, yet it also came with a crucial throwback to an earlier episode you might have missed — a throwback that likely tells us what exactly happened to Riley after the final flashback ended. Let's break it down.

What happens with Ellie and Riley in episode 7?

The main bulk of episode 7 is a flashback that shows us Ellie's life in a FEDRA training compound before she met Joel (Pedro Pascal). At the start of the episode we learn that Ellie's best friend Riley has been missing for three weeks. Ellie assumes she's dead, but she's wrong — in the middle of the night Riley sneaks in through her bedroom window and explains to Ellie that she's actually been recruited by rebel organisation the Fireflies.

The two sneak out together and visit an old mall which has been reconnected to the power grid without FEDRA's knowledge. They play around in the arcade, talk about FEDRA and the Fireflies, Ellie goes for it and kisses Riley to both of their delight, and their bond is tested by Riley's revelation she's leaving the next day for a Firefly post in Atlanta. And then, right at the end, tragedy strikes: the pair are blindsided by an Infected which they manage to kill, only to then realise they've both sustained bites while fending it off.

In the final shot of the flashback, Ellie and Riley sit huddled together in tears, promising to go on until they can't go on anymore.

The thing is, we already know what happens to Ellie after this — she's immune from the cordyceps infection, and the bite she sustains that day is nothing but an old scar by the time she meets Joel further down the road.

But what happens to Riley? The answer may lie in a conversation that takes place between Ellie and Joel back in episode 4.

Ellie's final moments with Riley link back to a scene in episode 4.

Remember when Joel and Ellie get ambushed in the Kansas City QZ by Kathleen’s militia on episode 4 and have to team up to kill that guy Brian who's trying to kill Joel? Yep, it's a while back, but stick with us for a moment.

After they've escaped to relative safety, Joel and Ellie have the following exchange:

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Joel: "The thing is I didn't hear that guy coming. You shouldn't have had to...you know..."

Ellie: "But you're glad I did, right?"

Joel: "You're just a kid. You shouldn't know what it means, to...It's not like you killed him, but shooting...I know what it's like. First time that you, er, hurt someone like that. If you, er...when...I'm not good at this."

Ellie: "Yeah, you really aren't."

Joel: "I mean it was my fault. You shouldn't have had to. And I'm sorry."

Ellie: "It wasn't my first time."

Joel doesn't ask anymore questions, so in episode 4 we're left wondering what exactly Ellie means by this. She's hurt someone before? Killed someone before? Was it a living person or an Infected?

We don't know for certain, but it seems likely that episode 7 gives us the horrible answer to this question. Ellie wouldn't have had many opportunities to kill between the FEDRA training compound, being found by Marlene and the Fireflies, and her meeting with Joel, so it's probable that she's referring to Riley in this exchange.

The tragic implication? Ellie watched her best friend succumbing to infection before ultimately being forced to kill her when Riley finally turned.

The Last of Us is now streaming on HBO Max.New episodes air every Sunday at 9 p.m. ET on HBO.