This season of Pretty Little Liars seems to be filled with reappearances from characters we've kind of forgotten about. For example, who is Nicole on Pretty Little Liars? On Tuesday night's episode of PLL, Ezra received a call from "Nicole," his ex-girlfriend that went missing while they were on their trip for Habitat for Humanity. Aria picked up the call but only heard background noise and after talking to Emily decided it was best to delete the call and not tell Ezra about it because surely that won't come back to bite her at some point.
You may have forgotten but Nicole first showed up in Rosewood because she was friends with Emily. She originally appeared in Season 6 to ask Emily if she wanted to go to Thailand with Nicole for a new Habitat for Humanity project. Emily turned it down to be with Sara, which Emily probably regrets now, and Nicole ended up going with Ezra who finally realized Rosewood is literally the worst place to live. Why any of these people keep coming back to Rosewood remains unseen. It's as if they want to die.
After the time jump it's revealed that Ezra and Nicole had a pretty serious relationship that mostly consisted of going to different places around the world for Habitat For Humanity. It was in Colombia that Nicole was either kidnapped or murdered by rebels opposing the current government. Luckily for Ezra he had gotten sick and left South America before the rebels attacked, hence why he is still very much alive and had a bit of survivor's guilt for a while there.
However, now it seems Nicole may just be alive after all. Although we couldn't hear her voice on the phone call the fact that someone did call from Nicole's phone after all this time seems to indicate Nicole will be back. This is Pretty Little Liars and on this show there's no such thing as a coincidence and now that Ezra proposed to Aria it makes sense that Nicole will suddenly pop up and ruin everything.
If Aria's smart she'll tell Ezra about the ghostly phone call, otherwise Nicole might just come back and tell him herself.