Renard (Sasha Roiz) tells Nick (David Giuntoli) and Hank (Russell Hornsby) he will leave for Europe to discuss the family crisis.
The stories state that through lack of better understanding of the cause, they presumed perhaps some kind of Wesen spirit would invade a child's body, and if said Grausen were left to grow into adulthood they'd invariably become much feared psychopaths wreaking total havoc.
While investigating in the books, Juliette (Bitsie Tulloch) finds that as there were high blood cell count, fever and his stressed immune system, they may be dealing with an infectious disease.
Recalling a study made by a colleague, Juliette deduces that perhaps the kid is infected by some kind of rare parasite similar to toxoplasmosis and if so, if they can find a way to kill the protozoa inside Daniel, the illness/behavior will stop and they could save him before more drastic actions are taken against him by 'The Council'.
Alexander gives the records to De Groot while Nick writes his notes on the diaries, adding that: Subsequent tests proved that hypothermia is able to kill the unicellular eukaryotic organism, identified as Daemoni Adspicio, which is the cause of 'Grausen'.
Grimm had already dealt with a case involving a church last year in 'The Good Shepherd' that amounted to one of the worst episodic tangents of the season.
And nothing makes The Exorcist look terrifying like lame network television appropriating the bare bones of an exorcism plot, which is what every promo suggested.
I've really come to enjoy the episodes that expand the scope and richness of the world; these entries might not propel the main plot forward, but they do expose the history.
'El Cucuy,' this week's 'Stories We Tell Our Young' seemed to have everything, swiftly putting Grimm back on track with its big theme for the season sans zombie-flashback-Nick.