'Supergirl': Kara Reveals Her Identity to SPOILER in "Blood Memory

Supergirl's secret identity has been a major issue on The CW series this season, especially with Colonel Haley determined to discover it and while last week extraordinary lengths were taken to keep it, well, secret, this week the Girl of Steel reveals herself to one specific person -- for a very good reason.

Spoilers for tonight's episode of Supergirl, "Blood Memory", below.

Sisterhood and secrets played a major role tonight. For Kara (Melissa Benoist), Alex (Chyler Leigh) no longer knowing that she's Supergirl was difficult. Not only did Alex have some memory issues, forgetting important things such as Kara's favorite movie, but being professional strangers and experiencing Alex's coldness was straining as well. Meanwhile Nia (Nicole Maines), along with Kara, visited her hometown and family where Nia's kept her Dreamer powers a secret from her sister Maeve (Hannah James). Maeve had expected to inherit the gift and is growing concerned that it hasn't happened yet.

And she soon discovers why. After the sudden death of their mother Isabel (Kate Burton), Nia reveals her powers when she saves Maeve from an attack by the Children of Liberty. The revelation does not go well, with an upset Maeve lashing out that Nia isn't a "real" woman. On the drive back to National City, Kara tries to support Nia in her time of need and realizes that the best way to do that is with the truth.

Kara stops the car and reveals to Nia that she is herself not only an alien but is Supergirl. She does this to try to help Nia believe that her sister will eventually come around and accept Nia fully -- just as, at one point before the mind wipe, Alex did her. She also tells Nia that she trusts her because Nia, too, is a hero. She only has to embrace it.

It's a revelation that Nia seems to take to heart sooner rather than later. At home alone later, Nia finally opens up a box that her mother (via her father) gave her, revealing that it contains the Dreamer super suit.

"I'm so excited. I'm trying to conduct myself on set in a professional manner and be like 'I'm not completely obsessed with the super-suit,' but it's all I think about," Maines said during a visit to the Supergirl set. "Every morning I wake up, 'I'm getting a super suit!' I'm going to sleep, 'I'm getting a super-suit!' I'm really, really excited. It's gonna be gorgeous! I have the best super-suit. I do."

Supergirl airs Sundays at 8 p.m. ET on The CW.