Secret, real name Greta Hayes, was Harm's beloved sister.
In life, Greta was a pretty prepubesent girl with long blonde hair held back in a hairband and green eyes. As a ghost, her skin tone, hair and eyes became paler. She wore a completely white, hooded, cloak-like dress over a black sweater, and white shin-high boots over slate blue stockings.
Both alive and as a ghost, Greta wore a silver pendant.
Greta was Harm's younger sister. She was the only thing he loved, but he had to cut her out of his heart by killing her in order to become "pure". Artemis speculated that the last thing Greta saw was the broken neon sign of Abel's House of Secrets across the street of her backyard, specifically, the word "secret".
Somehow, upon her death, she became 
On Halloween, Greta helped Artemis and Zatanna escape from Harm several times, ultimately leading them to his home, where Harm became suspicious and, rather than kill them as planned, took them captive.
Greta reappeared in the room in which Zatanna was held. She removed her gag, allowing Zatanna to free herself with her magic. Zatanna questioned Greta's motivation, but only received "secret" as a response.
After Zatanna and Artemis escaped from Harm, she floated out of her grave in the backyard. She showed them how her brother had killed her. She was the only thing he loved, and thus a weakness in his thirst for power. When Harm found them, she charged at him and took his heart away. This effectively resulted in his losing control of the Sword of Beowulf, and thus Artemis was able to defeat him easily.
With Harm defeated and bound, Zatanna promised Greta a proper burial and she disappeared soon after.
Powers and abilities
Greta had no apparent powers before dying. After her death, she became a ghost, and was thus intangible, had the ability to float, and disappear at will. She was also able to make an image of the dagger used by Harm to kill her, and  was able to touch small solids, such as Zatanna's gag and push a small fire escape.,
- 118. "Secrets"
- Secret was introduced in the original Young Justice comic series, in which she played a primary role from the beginning. Like in the show, Greta Hayes was the sister of Harm, who was killed by her brother as a sacrifice for power. Unlike the show however, she did not merely become a ghost, but was instead a "warder of Death", a gas-like spirit that could travel between life and death. She was for a large part responsible for the first official team-up of Young Justice, having been saved by Robin (Tim Drake), Superboy and Impulse (Bart Allen) before joining the team. Greta would later join the team officially, until being corrupted by Darkseid, and later rendered human by him.
- This is her first animated appearance.
- ↑ Weisman, Greg (2012-02-13). Question #14337. Ask Greg. Retrieved 2012-02-13.
- ↑ 2.0 2.1 2.2 David, Peter (writer) & Oliva, Jay (director) (November 18, 2011). "Secrets". Young Justice. Season 1. Episode 18. Cartoon Network.
- ↑ Weisman, Greg (2013-03-20). Question #19581. Ask Greg. Retrieved 2014-03-20.
- ↑ Weisman, Greg (2012-02-13). Question #14345. Ask Greg. Retrieved 2012-02-13.