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Template:Episode Quote "You Don't Know Jack" is the twentieth episode of Season 4 of Grimm and the eighty-sixth episode overall. It first aired on May 1, 2015 on NBC.


Press Release

A SERIES OF CONNECTED MURDERS LEAD EVERYONE TO THINK A COPYCAT IS ON THE LOOSE - GARCELLE BEAUVAIS AND NICO EVERS-SWINDELL GUEST STAR - A string of homicides have the press asking Captain Renard (Sasha Roiz) if a Jack the Ripper copycat has arrived in Portland. While dealing with the investigation, Nick (David Giuntoli), Hank (Russell Hornsby), Monroe (Silas Weir Mitchell) and Wu (Reggie Lee) deal with a situation they never expected. Meanwhile, Adalind (Claire Coffee) and Rosalee (Bree Turner) must work together on a last ditch attempt to fix Juliette's (Bitsie Tulloch) condition. Elsewhere, Juliette decides to help her new ally even if it means hurting those around her.

Guest stars

Nico Evers-Swindell
Garcelle Beauvais
Danny Bruno
Bud Wurstner



Select scene

Grimm - The Hexenbiest Is Here to Stay (Episode Highlight)

Grimm - The Hexenbiest Is Here to Stay (Episode Highlight)

Production Notes


  • Renard's bleeding side effect from his mother saving his life reoccurs.
  • Bud meets Adalind for the first time.
  • The first female Klaustreich is seen.
  • The trailer is badly damaged, but not all of its contents have been destroyed; subsequently, the remaining items, including some of the Grimm diaries and weapons, are moved to the spice shop basement.
  • It is revealed that Lauren Castro did not succeed in her campaign to become the mayor of Portland.


  • The names of the sent and received emails on Nick and Juliette's computer are of writers and other crew members for the show.
  • The last names of the first two murder victims, McDunnah and Casey, both are of Irish Gaelic origin; the killer, Jack, also has an Irish accent and sings an Irish folk song after he kills Henrietta.


Start a Discussion Discussions about You Don't Know Jack

  • Jack

    6 messages
    • Sean and Jack are Irish and English variations of the same root name of John are they not? Are Renard and Jack a sort of Jekyll and Hyde? ...
  • Episode 420 - "You Don't Know Jack"

    338 messages
    • (P) Macabros77 wrote: 4 days ago I made a comment about the e-mail . But it doesn't matter which  the real facts are. ...
    • LCD2YOU wrote: (P) Macabros77 wrote: 4 days ago I made a comment about the e-mail . But it doesn't matter which  the real facts are. ...
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