There’s a long-held secret that’s dramatically disclosed in the two-part seeaso finale of “Younger” starting Wednesday — with the ensuing chain reaction forever changing the power structure of Empirical Publishing.

“The fans are going to lose their minds,” says Molly Bernard, who plays publishing publicist Lauren Heller. “It’s really nuts what happens. There are two big things that happen right at the very end of the season.

“I think fans are going to be angry that we’re not on right away.”

The first revelation follows an unexpected company visit to the annual Frankfurt Book Fair (“It’s like Buffalo with dumplings,” quips Miriam Shor’s Diana Trout). With Charles Brooks (Peter Hermann) looking for funding from finance expert Quinn Tyler (Laura Benanti) to keep his publishing house afloat, the stakes are high: there are only three months of operating expenses left.

For her part, Liza (Sutton Foster) feels that lying about her age is about to catch up with her and she’s ready to come clean to protect the Millenial imprint, especially with rival publisher Cheryl Sussman (Martha Plimpton) on the scene. Sussman knows Liza’s deal and she will only keep the secret if Liza makes a deal with her.

Bernard was shocked when she read the script and learned Liza’s decision. “Liza’s done a good job of maintaining her life, but I’m so happy she came clean,” she says. “The show gets more interesting because she does.”

The second surprise happens at an impromptu dinner party hosted by Maggie Amato (Debi Mazar) in Williamsburg, Brooklyn, where her girlfriend Malkie (Sally Pressman) floats the idea that Josh (Nico Tortorella) become a sperm donor for her. Lauren, for one, thinks it’s a great idea.

“It seems like innocent party banter, then Maggie sees that it’s not and she and Malkie both react,” says Bernard. “It’s a show about age. The message is: ‘I’m not getting younger.’ ”

To that point, the characters on “Younger,” which has been renewed for a sixth season — scheduled to back into production in March — realize what they need. Nico doesn’t see himself as a sperm donor but, in a dream sequence, as a family man, with Liza. Is he going to go for it?

“I kind of hope so,” Bernard says.

While her role on “Younger” is clearly a supporting one, Bernard is looking forward to a meaty role next month as an agent provocateur on “Chicago Med.” She plays Elsa Curry, an arrogant, third-year medical student who shakes things up at the hospital.

“ ‘Younger’ was my first job out of Yale Drama School,” she says. “I was expecting to be a downtown theater actress. But this is my first big network show. Network reaches a lot of people and it’s nice to spread messages to people on them. I feel very grateful. ‘Chicago Med’ reaches a very different kind of demographic.”