Niemi, who plays Jack Pearson’s (Milo Ventimiglia) mother, Marilyn, says her character’s journey as a working class woman who finds herself in an abusive relationship was difficult to play on an emotional level — but was familiar on a personal level.
“I tapped into some personal experience,” Niemi exclusively tells PEOPLE of how she prepared for the role. “I was in a relationship that was pretty toxic and just wanting to be able to get out and not having a voice. I was just in a dark place — I think a place a lot of woman have been in. I could relate to wearing those shoes when it came to Marilyn’s marriage to Stanley. Also the subject of alcoholism was relatable. I’ve seen what it does and the hostages are taken under that disease. I knew her journey was going to be a tough one.”
As far as Tuesday’s episode goes, Niemi says her “journey of now having two boys” will come into play, and viewers will soon see how the Pearson family dynamic impacts Jack’s life.
“This is a big episode for Jack,” she says. “There’s a lot of reveal on our family history. I think it’s going to be a pretty wonderful episode to be able to see how he became who he is. I think it starts with our parents.”
In the season 3 premiere last month, viewers were transported back to the ’70s and found out more about Jack and Rebecca’s first date.
“I always said I was born in the wrong era,” Niemi says about her character’s time travel. “My best friend growing up was my grandmother. This is her generation. I spent New Year’s Eve with my grandparents. I just feel like I’ve always had an older soul and that period of time was such an incredible time. It was wonderful to dive into that period of history.”
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And working alongside Ventimiglia has been far from dull.
“I’m on a show that everyone watches ,so people are constantly texting me, ‘What was it like?’ It was fun being able to feel the enthusiasm in my personal life as well,” she says. “Milo is my boy. He’s such a lovely and wonderful man. He makes my job so easy. He’s such a lovable guy and sets the bar so high with this character.”
As for what’s to come this season, the cast previously told PEOPLE that things will begin to fall together come midseason — with the obvious curveballs.
“Episode four is a doozy. We’re going to see a side of Kate we haven’t seen so far. Kate hasn’t felt her feelings deeply and a lot of them are bubbling to the surface. As humans, we don’t always know how to handle them or express them. Sometimes anger is sometimes just sadness masked,” said Chrissy Metz, alluding to Kate’s miscarriage last season as well as Toby’s battle with depression.
This Is Us airs Tuesdays (9 p.m. ET) on NBC.