'Grimm' fans can hold to their hats to watch the biest out of its deck in season 4 episode 21 titled 'Headache'.Video/Screenshot

"Grimm" season 4 will show the darker side of Juliette Silverton (Bitsie Tulloch) and the challenges faced by Nick Burkhardt (David Giuntoli) in episode 18 titled "Mishipeshu", scheduled for telecast on NBC next Friday, 17 April, at 8pm.

The detective is an expert in dealing with all kinds of supernatural forces but the toughest test in his life will be the relationship with newly-turned hexenbiest, who is gradually losing her humanity. 

After trying hard to embrace what she's become, the veterinarian will decide to take revenge on Adalind Schade (Claire Coffee). During her search for the former hexenbiest, Silverton will land on the wrong side of the law with her erratic behaviour. So it remains to be seem how Burkhardt will save his lady love from ending up in jail.

Meanwhile, the protagonist and his partner Hank Griffin (Russell Hornsby) will have to deal with a new case, which will take them to the dark and mysterious path of a local Native American power quest.

On the other hand, Rosalee Calvert (Bree Turner) and Monroe (Silas Weir Mitchell) will take up a new mission and call Captain Sean Renard (Sasha Roiz) for help in episode 18 titled "Mishipeshu".

Until "Grimm" tells the Native American mythologies of Great Lakes, fans of police procedural fantasy series can tune in to NBC this Friday, 10 April, at 8 pm to watch a rare wesen in episode 17, which will be live streamed here.