Born in 1996 in the village of Tetney in Lincolnshire, England, Henderson developed a love of music early, teaching herself to play the piano before the age of ten. She won a scholarship to the prestigious Tring Park School for the Performing Arts, where she boarded until she was 16. Almost immediately upon leaving school, she auditioned for The X Factor with her self-penned song "Missed." Earning a spot on the show's ninth season in 2012, she was soon a favorite to win but eventually lost out to James Arthur in the public vote. Her departure from the series was considered one of the biggest upsets in its history at the time and launched a slew of celebrity tweets in her support. Simon Cowell, for one, believed in her, signing her to his Syco label, after which she spent a year in the studio writing and recording her debut album. Some of her collaborators included Babyface, Salaam Remi, and OneRepublic's Ryan Tedder, who co-wrote her first single, the beat-heavy, retro-soul "Ghost." The song debuted at number one in the U.K. and Ireland, also charting internationally, including in the U.S., where it reached number 21 on the Hot 100. Her second single, "Glow," co-written and produced by Steve Mac, had a more electronic sound and again hit the U.K. Top Ten. The album Chapter One followed suit upon its release in October 2014, going to number one in the U.K. and number 11 in the States.
Following the success of her debut, Henderson become an in-demand vocalist in the EDM world. She landed on the Billboard Hot Dance/Electronic Songs several times with tracks including Kygo's "Here for You," a 2015 dance hit in the U.S. that reached the Top Ten of the singles chart in the U.K. Around that time, she reached the U.K. Top Five with "Glitterball," a duet with Sigma. In late 2016, Henderson finished recording an album with producer Max Martin that was ultimately scrapped, but she still supported James Arthur on his Back from the Edge tour in 2017. That June, she joined a group of artists that included Leona Lewis and Liam Payne on a fundraising cover of Simon Garfunkel's "Bridge over Troubled Water" that topped the U.K. singles chart. She next appeared on "We Got Love," a Top 30 dance hit in the U.S. for Sigala, and on "This Is Real," a 2019 collaboration with Jax Jones that reached number nine in the U.K. as well as the Top 30 of the U.S. dance/electronic songs chart. In November of that year, she released her first solo material in four years, the EP Glorious, which arrived on Asylum/Atlantic.
In 2020, Henderson was featured on yet another Top 30 dance hit, Sam Feldt's "Hold Me Close," and that June she returned with the solo track "Take Care of You." It was co-written by Henderson and pop heavyweights Julia Michaels, Justin Tranter, and Noel Zancanella. That year, Henderson also co-wrote the U.K. Top Three hit "Lighter" by Nathan Dawe. In 2021, she had a Top Ten hit of her own with the Tom Grennan duet "Let's Go Home Together." Several years in the making, and featuring contributions from over a dozen producers, her first album-length release in eight years, Everything I Didn't Say, was issued on Asylum in March 2022. It debuted at number eight in the U.K. ~ Marcy Donelson & John D. Buchanan, Rovi