Next week on "Grimm," get ready for the penultimate episode of Season 4! The hit NBC series returns next Friday, May 8 at 8:00 p.m. EST with "Headache" (S04E21). Get ready for an entertaining show! Spoilers reveal that Trubel (Jacqueline Toboni) will be making a surprising return to Portland! Care for some more "Grimm" updates? Keep reading for a full Episode 21 synopsis, and more spoilers below!

"Grimm" fans, what should you look forward to seeing on next week's exciting penultimate episode of Season 4? Warning: Episode 21 spoilers ahead!

Luckily, the folks over at NBC have done us all a huge favor and provided us with the synopsis for Season 4, Episode 21.

"The manhunt continues for a vicious serial killer," teases the NBC press release. Plus, "Jacqueline Toboni returns as 'Trubel,'" the network announces.

Need some more details? We've got you covered!

According to the official synopsis for "Headache" (S04E21), "While investigating a grisly murder, Nick (David Giuntoli) and Hank (Russell Hornsby) get closer to uncovering the identity of the serial killer while Wu's (Reggie Lee) life is put in grave danger."

"Having turned down Monroe (Silas Weir Mitchell) and Rosalee's (Bree Turner) offer, Juliette (Bitsie Tulloch) solidifies a new alliance as she works to get her revenge," continues the NBC synopsis.

"Elsewhere, Trubel (guest star Jacqueline Toboni) makes a surprising return to Portland, explains the "Grimm" Season 3, Episode 21 synopsis.

"Sasha Roiz and Claire Coffee also star. Nico Evers-Swinderll guest stars," concludes the NBC press release.

Are you excited for the penultimate episode of "Grimm" Season 4 yet? After reading the latest "Grimm" synopsis and spoilers, what are you thoughts on what's next? Sound off with your thoughts and theories about "Headache" in the comments section below!

"Headache," Episode 21 of "Grimm" Season 4, airs Friday, May 8 at 8:00 p.m. EST on NBC.