Present-day Barry (Grant Gustin) will find out about his secret future message to Rip Hunter (Arthur Darvill) in next week’s highly anticipated crossover event between “Arrow,” “The Flash,” “Supergirl” and “Legends of Tomorrow.”

During a press visit to the Vancouver set of “Legends of Tomorrow,” series actor Victor Garber revealed to TVLine and other news outlets that the message Rip Hunter (Arthur Darvill) received from a circa 2056 Barry will get back to the source at some point during the crossover event, titled “Invasion!”

“It’s a big mystery and a big deal,” Garber said of the secret message (via Comic Book Resources). “It’s a spoiler if I give you too much information, but it’s just part of the whole mystery of time travel and the fact that this is coming from Barry years later and then when he finds out … it just sort of unfolds as these things do on these shows, and lots of things occur in that time period.”

Stein (Garber) and Jax (Franz Drameh) learned about the message from future Barry when they stumbled upon a hidden armory inside the Waverider in Season 2, episode 2 of “Legends of Tomorrow.” The dire message was only intended for Rip and forbidden for the crew, so the pair decided to keep it secret from their fellow Legends.

Although Garber couldn’t disclose too much information about the message, Garber did say that keeping it hush-hush will create a more complicated relationship between Garber and Jax. “Stein is saying, ‘We can’t tell them’ and Jax is saying, ‘Why can’t we?’” Garber said. “It’s kind of like a father and son: some days it’s good and some days you just want to say, ‘How did you become my child?’ which is also — for me, as an actor — what’s fun about doing it.”

The four-night crossover event, which is also called “Heroes v. Aliens,” kicks off with “Supergirl’s” Nov. 28 episode and continues on “The Flash” (Tuesday, Nov. 29), “Arrow” (Wednesday, Nov. 30) and “Legends of Tomorrow” (Thursday, Dec. 1). All four shows air at 8 p.m. EST on The CW.