Caroline "Caz" Hammond was the ex-fiancée of Kate Connor and a former serving soldier in the British Army. The two girls met in April 2015. Theirs was a whirlwind romance, becoming serious on their second date and they soon became engaged.
Caz's job meant long periods apart and Kate was therefore delighted when Caz was given leave at the time of her twenty-sixth birthday in November 2015, arriving in Weatherfield on a surprise trip from abroad arranged by the Connors. Kate's father Johnny had arranged a table at Nick's Bistro where both girls were toasted by family and workmates. The next day, with Johnny's consent and good wishes, Caz told Kate that she wanted to set a date for the wedding in April 2016 - a year after they had met. Kate accepted, seemingly happy, but she had just been confessing to Michelle Connor that the intensity of their relationship scared her as in the past seven months they had just had three weeks together. Her flying visit over, Caz left Weatherfield and reported back for duty.
Caz returned again in April and became concerned about Kate's friendship with Sophie Webster, worrying that something more was going on between them. Caz followed Sophie and gave her a threat to stay away from Kate even though Sophie insisted they were just friends. A few days later, Kate told Caz she wanted to postpone the wedding which Caz immediately assumed had something to do with Sophie and told Kate the wedding was off. Later that day, Caz caught Sophie and Kate kissing and Kate's pleas that it didn't mean anything were unsuccessful. Caz departed once again, adamant that her and Kate's relationship was over.
Later that month, Caz injured her ankle and returned to Weatherfield to be looked after by Kate. Sophie became suspicious of Caz's injury when Caz lied that Sophie had knocked her. Kate and Caz got back together but Kate also became suspicious when she overheard Caz talking to her support officer on the phone. Caz's jealousy continued and was once again convinced that Sophie was after Kate and also suspected Kate of having a romantic interest in Maria Connor.
In July, Maria's boyfriend Luke Britton also began to suspect something about Caz and after finding her painkillers in the sink, he knew she was faking her injury. Caz's welfare officer confronted her about a court martial proceeding and why Caz was missing her physiotherapy so Caz asked Kate to run away with her. When Clayton Hibbs started hitting on Kate, Caz attacked him, exposing her fabricated injury. Caz told Kate that she pretended her injury was worse than it really was because she wanted to be with her and also admitted that it wasn't caused by an accident but from a fight with another soldier. Having had enough of her lies, Kate broke up with her and told her she didn't want to see her again.
Caz was able to gain sympathy from Maria who let her stay with her in her flat. Luke did not approve and Caz's presence strained their relationship causing them to eventually break up. Maria ordered Caz to leave but a few weeks later found her sleeping rough on a bench. Caz revealed that she didn't get on with her parents and she had been discharged from the army, however Maria refused to let her move back into the flat. Caz manipulated Maria into letting her stay by sending a burglar to break in and scare her. Caz struggled to find a job and soon found herself in love with Maria. She made attempts to charm Maria and turned down a job in Newcastle in order to stay with her. After Caz's repeated attempts to get closer to her, Maria outright told her that because she was straight, there would never be any mutual feelings between them. Maria was due to visit London and told Caz she wanted her out of the flat by the time she returned.
Caz got a hold of Maria's new credit card, followed Maria to London and started spending money on it to make the purchases under Maria's name more plausible. One of the items she bought was a mobile phone which she used to send abusive messages to herself. When Maria returned home in late October she was horrified to find blood splattered on her wall and Caz missing. Kate believed that Maria had seriously harmed her after hearing a distressed voicemail from Caz. Investigators instantly suspected Maria of murdering Caz and hiding the body when in reality Caz was living in a bedsit and spying on Maria with a webcam. Caz fabricated more evidence by cutting herself with Maria's scissors.
In November, with Maria facing a murder trial, Kate's brother Aidan spotted Caz working in a factory but she escaped before she could be caught. A few days later, Kate realised that Caz was spying on Maria's flat and told Aidan that she still loved her. Caz paid Kate a visit, hoping to get back together, but attacked Kate when she learned her confession to Aidan was a ploy to trap her. Aidan rescued Kate and the police arrested Caz.