In last week's episode of The Blacklist, the moment Season 7 had been building toward came to pass, with Elizabeth Keen (Megan Boone) finding out that Maddie Tolliver wasn't some nice lady down the hall, she was really Katarina Rostova (Laila Robins), former KGB super-spy and Liz's mother. Katarina gave Liz up to protect her daughter from the people pursuing her, but it was still one of the formative traumas in Liz's life. And now, suddenly, her mother is back, and she's a threat not only to Liz, but to Liz's own daughter as well.

Liz's initial reaction to Katarina's revelation in this week's midseason finale will be "shock and anger," executive producer John Eisendrath tells TV Guide. "She has spent so much of her life looking for, asking about, wondering about, being told about this woman, but then to find out that this kindly, nice lady next door who's insinuated herself into her life and into the life of her daughter has been lying to her and is her mother, that is so hard for Liz to accept... As a mother herself, I think she's livid at what her own mother has done in her life and done potentially to her daughter, in exposing her daughter to danger."

The Blacklist Recap: A Trip to the Past Creates More Questions Than Answers

But once the initial shock has worn off, what Liz does about her mother's unexpected reentry into her life may surprise viewers. "Part of what is so difficult about what Liz is confronted with is that not only does she have this incredible anger and frustration and sense of betrayal that John's speaking about, but she's also standing face to face with a woman who has the ability to unlock answers and truths, and so she needs something from her," says creator Jon Bokenkamp. "As much as she wants to put a bullet in her head for everything she's done to her, she wants answers, and Katarina has answers. And so it makes for a very sticky situation in terms of emotionally how to handle this confrontation, and I think the audience is going to be surprised in terms of how that relationship builds out in this midseason finale."

The Blacklist's Season 7 midseason finale airs Friday, Dec. 13 at 8/7c on NBC.

Megan Boone and Laila Robins, <em>The Blacklist</em>Megan Boone and Laila Robins, The Blacklist