9-1-1 star Corinne Massiah previews May's biggest test yet

May Grant is in danger.

In "May Day," the 118 must save May (Corinne Massiah), Claudette (Vanessa Estelle Williams), and others after a fire breaks out at the 9-1-1 Call Center. Described as a "heartbreaking tear-jerker," Massiah explains that the fire at the call center will test May like never before and put things, including her relationship with Claudette, in perspective. "She is really tested, and it shows how much she's grown as a person and puts a lot of things into perspective about what matters in life," she teases. Massiah calls the new episode — of which EW has an exclusive preview below — her favorite one for May to date.

The young 911 operator's growth is front and center in the hour because, unlike in past emergencies, she has to figure out how to survive without Athena and Bobby. "When the call center is on fire, she has to flip off that switch and can't be emotional because she has to think logically in order to save herself. She has to go into fight mode," she says.

Not only was the episode a challenge for May, but also for Corinne. While she's been at the center of emergencies like season 3's tsunami, this put the young actress closer to the fire. "This episode just felt different to me," she shares. It was her first time with big fire sets and sets being demolished around her, and Massiah was happy to have Peter Krause's support. "He walked me through everything because it was intimidating and scary at first. I always felt comfortable on set," she shares.

Krause also made sure college student Massiah was okay on set and in the classroom. "We had some overnight shoots, and [Peter] would make sure I was okay. He'd say 'we have a [4 pm] to 4 am so if you have a test study before.' " Athena (Angela Bassett) and Bobby's (Krause) relationship has provided the opportunity to see a wonderful relationship between May and Bobby blossom. "[Peter] is literally Bobby in real life. He's so easy to talk to," she says, "He talks to me about college as Corinne, and those conversations are almost direct reflections of May and Bobby's."

May's journey has been one of the most significant evolutions on 9-1-1. Athena fought to save her daughter's life when the series began after a suicide attempt. Now May's thriving professionally, has a strong family unit, and has an acceptance to USC, which she has to make a decision about very soon. Corinne remembers being nervous when she learned May would become a 911 operator. "It was a big transition to go from being the kid sitting at the dinner table to being a kind of first responder taking really dramatic and emotional calls," Massiah shares.

Massiah is proud to have grown with May and has found that they have been going through the same things simultaneously. Shortly after Corinne had conversations with her parents about applying for college, May talked to Athena and Bobby about it on screen. "I feel so connected to her to the point where it doesn't feel like I'm playing her, but she's also challenging me and changing my perspective about life and how I deal with people."

911 operator Claudette presents a new challenge for May at work. While Corinne has enjoyed working with Williams, May has learned some hard lessons from Claudette. "May's learning not everyone is going to like her off the bat, and that's okay," Massiah says, "May needs to reevaluate her priorities and her when of thinking when in the call center because it's not about everyone liking you, but saving lives." The question is can these two put their differences aside to survive the emergency at the center of the new episode of 9-1-1.

Messiah feels honored that Juan Carlos Costa, who wrote and directed the episode, believed in her and named an episode after May. "I got to let my emotions loose and test my ability as an actor. It really made me love my job, so I'm excited for everyone to see this episode," she says.

9-1-1 airs Mondays at 8 pm ET on FOX.

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