Candace Stone was initially a recurring character in the first season of You, though she is only being shown as flashbacks and hallucinations. She was promoted to series regular and serves as the antagonist from Joe's perspective in the second season. She is portrayed by Ambyr Childers.
Candace was an aspiring musician, who had a relationship with Joe prior to the start of the first season. Throughout the first season she is considered to be missing and mostly appears in flashbacks, hallucinations, and conversation- until she shows up in the final episode.
We learn that Candace cheated on Joe and later left him, telling him she never loved him. In an attempt to restore their love, Joe kidnapped her and drove her to a remote area where they had previously spent time together. He presented her with a picnic and tried to reason with her that they should continue their relationship. When she tried to run and fight back against him he slammed her head, knocking her out. Believing he killed her, he buried her in a shallow grave topped with flowers and left . She woke up, crawled out of the dirt and went to a police station to report the incident. Since she had no evidence of her claims that he had tried to kill her, there was nothing that they could do. She then disappeared, leaving without saying anything to her friends or the only family member she had, her twin brother who is in a mental facility. Her brother apparently believed she was dead and that Joe murdered her. According to Joe, her brother was insane, believed Joe was a spy, and Candace had him committed. He died while in the facility. We are left to wonder what involvement Joe had in having him committed for coming between them.
Candace shows up unexpectedly in Mooney's book store, having read Beck's book The Dark Face of Love, and suspecting Joe had been involved with her. She threatens to expose Joe and make his life miserable as punishment for what he did to her. After he disappears to LA, she finds him and inserts herself into his life by begging a relationship with Forty Quinn under the name Amy Adam. She claims to want to protect the Quinns from Joe and vows to watch him until he slips up and expose him because "murder has a way of following him".
Love becomes suspicious of her and has a private investigator look into her, discovering she is actually Candace Stone, and confronts her as she breaks into Joe's apartment. Candace tells Love all about who Joe really is and that she is there to protect her, showing her a picture of her and Joe together. She accepts a pay off from Love to leave and Joe is able to convince the Quinns she was an obsessive ex and he had left New York and changed his name to get away from her.
She doesn't leave as she promised Love. Instead, she continues her involvement with Forty which inadvertently leads her to Joe's storage locker where he keeps his glass cage. She discovers him in there with Delilah's corpse. She locks him in and rather than calling the police, she messages Love from Joe's phone telling her to meet him there. She tells Love this is what Joe really is and that she wanted her to see before she turns him in. To her surprise, Love kills her by cutting her throat with a broken bottle.