This post contains mild spoilers for The Flash season 4
The Flash returned for its fourth season tonight, but it did so without one of season 3's chief characters, Julian Albert, and we now know why. Former Harry Potter actor Tom Felton played the character throughout The Flash season 3, first starting out as one of Central City PD's top crime-scene investigators and eventually turning one of the season's big bads: Doctor Alchemy. Of course, he wasn't inherently villainous, and the Flash eventually managed to save him.
As atonement for his actions while he was the supervillain, though, Julian joined Team Flash and helped the crime-fighting team apprehended and defeat the supervillain Savitar. At that point, Julian had become an invaluable member of the team, and they wanted him to remain on for the long haul. He was even willing to work alongside the Flash in the season's future episode as well. Unfortunately, it was revealed over the summer that Felton wouldn't be returning as a series regular for season 4, despite the character starting to click with the team towards the end. Series showrunner Todd Helbing promised that audiences would quickly learn what happened to Julian, and it looks like Helbing has kept his word.
In the opening minutes of The Flash season 4 episode, "The Flash Reborn," Detective Joe West (Jesse L. Martin) tells Iris West (Candice Patton) that the police department's crime lab had been swamped ever since "Julian moved back to London." Considering that Julian was the only other crime lab technician working at the CCPD aside from Barry Allen (who had disappeared into the Speed Force in the season 3 finale), it seems that CCPD may be looking for another CSI.
Although Julian's (and Felton's) absence will be felt throughout the season, it's still possible that he could return in the future, even as a series regular. After all, reports have only indicated that he would no longer have a series regular role (which can be constricting for working actors and actresses), not that he would never return to the series. Since his character has simply returned home, he could always come back to Central City if Team Flash really needs him. And with Barry coming back after spending months trapped in the Speed Force, he will certainly need some time to adjust before getting back into action - both as the Flash and as CCPD's chief CSI.
While Julian is gone (for now), there's no shortage of exciting things to look forward to this season, such as Barry getting a new power as well as the techno-organic villain Kilg%re joining the fray.
The Flash season 4 airs Tuesdays @8pm on The CW. Arrow season 6 premieres Thursday @9pm on The CW.