We know that Spencer Hastings (Troian Bellisario) has a big secret related to the night Ali disappeared, and many fans wonder if she did something bad to her former bestie. While tonight's episode, Season 4, Episode 19 ("Shadow Play") didn't give us a straight answer about what happened way back when, it did take us into Spencer's mind, and dropped a few hints that make us wonder if Spencer really did hurt Ali that night.

As Troian Bellisario told us, Spencer has a lot of guilt built up about the night Ali disappeared. We know she and Ali had a fight — but did more go down than we've seen? Here are the moments from Episode 19 that make us worry that Spencer's secret is something truly dark.

1. "Maybe you should be the one I'm afraid of." When noir Ali came to noir Spencer in her house, Spencer got frustrated and demanded Ali give some straight answers. "That is a scary look, Spencer," Alison accused. "Maybe you should be the one I'm afraid of." Is that Spencer's unconscious admitting to itself that Ali has a reason to fear Spencer?

2. "Smart enough to get away with murder?" In the follow up scene, after Toby found Spencer desperately reached for more pills and took her to an integration room, he mockingly told her, "Spencer doesn't get confused. Spencer's the smart one. Maybe smart enough to get away with murder." "Maybe," Spence replied.  

Of course, then Toby followed up with: "Or maybe smart enough to help Ali fake the whole thing," another popular fan theory. Does Spencer even know what really happened that night?

3. "This one already tried once!" When the Liars finally found Ali, she wasn't happy to see them. "Are you trying to get me killed?" she asked. Then she pointed a finger at Spencer. "This one already tried once." The tension was palpable, and we have to wonder if this was a clue.

4. "Are you sure about that?" In the same scene, Aria told Ali that the Liars want her back. "Are you sure about that?" she questioned. Again she turned to Spencer. "I bet this one would love it if something happened to me. That way she shouldn't have to worry about dropping down to second place if I came back."

Clearly, Spencer does have conflicted feelings about Ali, and is harboring guilt about that. But are these moments a sign that she has more to feel guilty about than not always loving Ali?

What do you make of these moments? Are they hints about Spencer's secrets, or red herrings? Share your thoughts in the comments below!

Rebecca Martin is an Associate Editor at Wetpaint Entertainment and our resident Game of Thrones, Breaking Bad, and genre TV expert. Follow her on Twitter and Google+!