Jesse Spencer explains Matt Casey's 'Chicago Fire' return, why his ex was shocked: 'Rough call'

Jesse Spencer returns to "Chicago Fire" and turns up the heat in his station house homecoming.

The Australian actor, 44, portrayed Matt Casey on the Dick Wolf drama for nine seasons, leaving in Season 10. Casey moved to a new life and new captain's job in Portland, Oregon but returned for the Season 10 finale wedding of Kelly Severide (Taylor Kinney) and Stella Kidd (Miranda Rae Mayo).

"Matt was the best man, so it was appropriate to return," says Spencer.

Now, urgent fire business and discussions with a past flame bring Casey back to Firehouse 51 and local hangout Molly's for Wednesday's episode (now streaming on Peacock).

"I always said that if you ever want to bring Casey back down the line, I'm open to it," says Spencer. "And it's fun, because they put me in the middle of a heap of stuff that stirs things up."

Here's the fallout from Casey's "Chicago Fire" return.

Why did Jesse Spencer leave 'Chicago Fire'?

Spencer, who starred as Dr. Robert Chase on the Fox medical drama "House" from 2004-12, was a fan favorite during his decade-long "Chicago Fire" run. But Spencer's life priorities changed with his 2020 marriage to neuroscientist Kali Woodruff Carr and the birth of the couple's first child.

"I got married and had a toddler. So things shifted in my life," says Spencer, who left for personal reasons after his 200th episode, but still lives in Chicago.

He still has his "Chicago Fire" helmet and keeps his firefighter Halligan bar forcible entry tool in his apartment. "You never know when you're going to need one," he says. When his child was stuck in the apartment building elevator earlier this year, Spencer immediately considered prying the elevator doors open himself.

"I nearly ran upstairs and grabbed my Halligan," says Spencer. "But then I figured the building HOA wouldn't appreciate me busting open the doors. So I called the fire department. They came and got my child out."

Matt Casey has 'Chicago Fire' business and unfinished love

Casey has urgent business: alerting Kidd to a secret Department of Homeland Security and FBI task force recruiting key first responders to prevent domestic terrorist attacks.

"Stella is his prodigy, He's watched her grow as a firefighter and encouraged her to take a leadership role," says Spencer. "So that's his first pick."

But the real heat comes between him and ex-flame paramedic Sylvie Brett (Kara Killmer), who is visibly shocked by Casey's return.  "That was a really rough call by Casey, just appearing," says Spencer. "But things were happening really quickly."

The two officially called off their relationship earlier this season by phone, and Sylvie is dating Dylan (Christopher Allen). But the Casey-Brett sparks fly with intense eye contact during a late night meeting at Molly's that ends with a nine-second (we timed it) full embrace.

"Even though they've broken up, he still has a lot of love for the girl," says Spencer. "I still wonder if that's the real reason he came back: for her. She's in a relationship, and he'll stand down. But he wants her to know he's still there. He's like the ghost of Christmas past."

Casey was not able to catch up with Severide, who has been called out of state on assignment (Kinney is taking leave from the show for personal reasons).

Matt Casey gets into 'Chicago Fire' rescue action

It wouldn't be a homecoming without Casey returning for a fire shift. He's still a whiz at putting on cumbersome safety gear during drills.

"I knew right where the buckles and straps were, just like riding a bike," says Spencer. "The only thing I forgot was how heavy that gear is. And you're taking it on and off for scenes, like 30 times. I didn't miss that."

Of course, the crew is called out on Casey's former rig Truck 81 to rescue a man hanging from a Chicago apartment building window.

"We went for a ride in the rig, like old times; it was fun," says Spencer. "It was like I never left the show."

Don't leave us hanging: Will Matt Casey stay at 'Chicago Fire'?

No. The "Chicago Fire" return is a guest appearance, and Casey will return to his new life in Oregon. But Spencer is eager to come back to his TV family soon. He's still close with castmates, including Killmer.

"She brought her family over and we all hung out; we're good friends," Spencer says. "This show was such a special part of my life for 10 years, so I'm always open to coming back."

Keep the 'Chicago Fire' burning:

• Jesse Spencer leaves: 'Chicago Fire' after 10 seasons, but there's 'potential' he'll return

• The wedding return: Jesse Spencer's Matthew Casey attends Severide-Kidd wedding on 'Chicago Fire'

• 'Chicago Fire' Taylor Kinney: Fields questions about ex Lady Gaga: 'I’m really proud'

• NBC schedule 2022: 'Chicago Fire,' Camila Cabello joins 'The Voice'; 'Quantum Leap'

This article originally appeared on USA TODAY: 'Chicago Fire' drama as Matt Casey returns: Jesse Spencer reveals all