In the Season 5 promo for The Vampire Diaries, we see Silas (Paul Wesley) flirting with Katherine (Nina Dobrev). What is Mystic Falls’ most recent Big Bad up to? What does he want with human-again Katherine? We speculate below.

She’s his way to the Salvatore brothers

Damon and Stefan more-or-less hate Katherine, but they also have a habit of tolerating her. Maybe it’s because she sired them. Maybe it’s because she looks like the woman they love. Whatever it is, Katherine has a talent for insinuating herself into the Salvatore mansion and into the Salvatores’ lives. Sure, Silas looks like Stefan, but Damon seems to figure out he’s not his brother relatively quickly, which means he could use someone on the inside. Katherine is probably willing and able to do this.

She has information

Katherine has been around a long time as in, centuries. Silas, on the other hand, has been asleep for a long time as in, millenia. Sure, he could just watch the first few seasons of TVD to catch up, or he could use Katherine as his informant. She probably knows more about the intricacies of the supernatural world both in Mystic Falls and beyond than any other person currently in town. That information is valuable, which is lucky for her, considering she no longer has her vamp powers to protect her.

She reminds him of his long-lost love

We’ve been working on this theory that the original Petrova doppelganger was Silas’ love who he aimed to make immortal. If that’s the case, then Katherine (and Elena) look like the love-of-his-life. Silas might not love them for that, but we could see the lonely old vampire wanting to keep someone like that around. Does Silas actually have a weak spot or is he all evil?

He wants her blood

We still don’t fully understand what it means to be a doppelganger, but doppelgangers occur to offset a supernatural imbalance, a disruption to the natural order of things. Because of this, they seem to have supernatural significance, i.e. Elena’s blood was used by Klaus to create his hybrids. Doppelganger blood only seem to have power when the doppelganger is human, which is why Katherine could play an important role in Season 5. Now that Elena is vampire, Katherine is the only human doppelganger in existence. That usually spells trouble for the doppelganger in question but it’s usually great news for villainous schemes.

Why do you think Silas is interested in Katherine? Share your theories in the comments below!

Catch the Season 5 premiere of The Vampire Diaries on Thursday, October 3, 2013, at 8 p.m. ET on The CW.