S4 interview with Rob Thomas によって Christina だいこん, 大根 for Collider, 2 Aug 2019.

"We’re referring to the sad, depressing — although, let’s face it, inevitable — conclusion to the budding friendship between Kristen Bell’s titular sleuth and Kirby Howell-Baptiste’s newcomer Nicole. " TVLine, 28 July 2019.

Lots of S4 spoilers, obviously, from デン Of Geek.