Marie de Guise (Amy Brenneman) will return to have an important talk with her daughter in episode 15 of "Reign" season 2.

Carter Matt posted the official synopsis of the upcoming episode titled "Forbidden." It reads: 

"Mary's (Adelaide Kane) mother (guest star Amy Brenneman) returns to advise Mary that her throne is in jeopardy. Mary makes a shocking proposition to Condé (Sean Teale), along with a bold move to reclaim her throne. Francis (Toby Regbo) moves closer to Lola (Anna Popplewell) after a setback with Mary, while King Antoine (guest star Ben Aldridge) makes Kenna (Caitlin Stasey) an interesting offer." 

Late last year, "Reign" executive producer Laurie McCarthy talked about Marie's visit in an interview with Entertainment Weekly. 

She said, "You never know what's coming with Marie de Guise, and this time will be no different as she delivers a series of shocking revelations to Mary, and ultimately forces her to face and confront her failing relationship with Francis." 

McCarthy also teased that in the upcoming return of Mary's mother in France, she will unintentionally bring an unexpected experience for one of her daughter's ladies-in-waiting. But the executive producer did not provide any other information about who that character is. 

Meanwhile, fans will also get to see the events that happen after Condé finds out that he is being blamed for poisoning the bible of Henry, something that his brother Antoine actually did. How will Condé deal with all these? 

Also, Condé and Mary's relationship is still uncertain in the coming episode. Will the two finally give in to their feelings despite all the odds? 

In other news, TV Line reported early this week that Queen Elizabeth will be joining the series as a regular character. Although the spoilers are still mum about who will portray the role of the young British monarch, she was described as someone who is "beautiful, cunning and brave, vulnerable and in love." 

"Reign" season 2 episode 15 airs Thursday, Feb. 19.