The "Chicago Med" series, set to make its debut later this fall, has added new characters in the wake of Laurie Holden's departure, who was supposed to be the show's main character.

The upcoming show is a spin-off of the drama, "Chicago Fire." Holden had been cast as Dr. Hanna Tramble, a troubled ER surgeon. She made her first appearance during the backdoor pilot aired last April. In that episode, a grenade exploded in the middle of the hospital.

"I am so grateful to Dick Wolf, my fellow cast members, NBC and the entire Chicago Med team for their understanding," Holden said. The actress stated that it was a tough decision but due to personal family reasons, she had to depart from the show.

In her place, three new characters will be added.

Torrey DeVitto was recently cast as a series regular. She will play Dr. Lilly Manning who is a pregnant emergency room physician.

Rachel DiPillo also joins the show as a series regular. She has been cast as Dr. Reese, a young first year intern, having only recently left medical school.

The producers have yet to cast the third female character, said to be a charge nurse.

"Chicago Med" will chronicle the lives of a hospital team inside a busy Chicago hospital ripe with emotional chaos and explosive drama.

According to show runner and producer Dick Wolf, the freshman series will feature storylines that viewers would usually see in the headlines and will be informative for viewers tuning in.

"Every week you will get at least one piece of medical info you probably didn't know... Everything that touches on our medical or physical life is fair game for us," Wolf said.

"Chicago Med" will occur in the same universe as three other Dick Wolf installments. It will join "Chicago Fire," "Chicago PD "and "Law & Order: Special Victims Unit."

Viewers can also look forward to seeing their favorite Chicago characters interact with each other.

Co-creator, Matt Olmstead, confirmed during the Television Critics Association event that a four-way crossover event is likely.

"Yeah, there's a four-way crossover with [the] three Chicago shows and SVU – the jumbo crossover, never done before," he said.

The crossover event is slated for a February air date and will reportedly feature eight different storylines.

"We've done three crossovers so far. They're very daunting and ultimately, like any artistic endeavor, the most daunting ones turn out to be the most gratifying," he added.

"Chicago Fire" premieres on Nov. 17, Tuesday, at 10 p.m. on NBC.