Fiona Shaw Was Told the Plot of Bad Sisters Season 2 in '25 Seconds' Over Breakfast and Was Immediately 'Delighted to Join' (Exclusive)

It didn't take much to convince Fiona Shaw to join the Garvey sisters' gang.

The Harry Potter alum, 66, was a fan of season 1 of Bad Sisters when it premiered two years ago, and she tells PEOPLE that a less than one-minute pitch from creator and star Sharon Horgan and director Dearbhla Walsh was all it took to bring her onboard for season 2.

"Sharon and Dearbhla told me the plot in 25 seconds over breakfast one morning, and I kind of followed it, but whatever it was, I wanted to be part of that team," Shaw says. "And I didn't regret it for a second."

"I was delighted to join," Shaw adds. "I mean, season one had been just breathtaking."

Shaw says she "didn't know how they were going to go about season 2" after the first season ended with all the questions of JP's (Claes Bang) death revealed: Grace (Anne-Marie Duff) had enlisted the help of her neighbor Roger (Michael Smiley) to set her husband up on a four-wheeler and make his death look like an accident rather than the murder it had been.

It was a shock that Grace's sisters, Eva (Horgan), Bibi (Sarah Greene), Ursula (Eva Birthistle) and Becka (Eve Hewson), weren't actually involved in killing JP, who they'd long-since dubbed "The Prick," as they'd spent months at that point making valiant attempts to kill him.

Season 2 takes place two years after JP's death, with Grace and the Garvey sisters moved on, but "when past truths resurface, the ladies are thrust back into the spotlight, suspicions are at an all-time high, lies are told, secrets revealed and the sisters are forced to work out who they can trust," per the official synopsis.

Shaw, who joins as Angelica, Roger's nosy sister who forms a bond with Grace, teases that in season 2, Horgan "takes things right to the edge" just like she did in the first installment.

"She thinks of the most impossible thing, and then somehow swims her own way out of it through the writing," Shaw says. "It's very clever."

She continues, "Sharon writes for that group, so the wit of the girls is sort of infused into it, and all the eccentricities that went along — I think that we all put into it — then became part of the writing because Sharon is writing it all the time."

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The first 2 episodes of Bad Sisters season 2 are now streaming on Apple TV+. New episodes air Wednesdays.