Oh where, oh where can Derek (Patrick Dempsey) be? That seems to be the question on everyone’s mind -- especially Meredith’s (Ellen Pompeo) -- since episode 19 of “Grey’s Anatomy” concluded.

In the last installment, titled “Crazy Love,” it was revealed that Derek never made it to his meeting in Washington, D.C. This news came as a surprise -- and a bit troubling -- to Mer considering the last time her husband missed an important conference it was because his plane had crashed. (In Season 8, a handful of employees at Seattle Grace Hospital [including Meredith] were involved in a devastating aircraft collision, one that led to the demise of both Lexie [Chyler Leigh] and Mark [Eric Dane].)

To make matters worse, the morning following Derek’s disappearance, Mer will learn that an airplane crash has also occurred. Talk about déjà vu. The episode 20 synopsis for “One Flight Down” teases that the accident will bring back “horrible memories to the doctors,” particularly Mer and Arizona (Jessica Capshaw), who will suffer from PTSD.

In a sneak peek video for episode 20, audiences can see Mer (rightfully) freak out in “One Flight Down.”

“Any word?” Bailey (Chandra Wilson) asks Meredith, who is anxiously starring at her phone. After Mer breaks the news the Derek hasn’t reached out to her, Bailey tells Meredith to wait until five o’clock -- that’s when Bailey suggests Mer to start panicking.

Maggie (Kelly McCreary) overhears the conversation and asks her half-sister, “What’s at five o’clock?”

“Derek missed his meeting in D.C. this morning,” Meredith reveals. “I called him and he didn’t pick up and I haven’t heard from him all day. Five o’clock is my deadline -- if there’s no news then I’m going to go home and freak out.”

But Maggie can see the fear has already begun to set in as her sister clings to her cell. That’s when fans get to witness an intimate scene between the two scrub-donning daughters of Ellis Grey (Kate Burton):

Where do you think Derek is? Could he be a victim to another plane crash? Sound off in the comments section below with your theories before episode 20, “One Flight Down,” airs on Thursday, April 16, at 8 p.m. EDT on ABC.