"90210" returns with an all-new episode tonight, but first the cast of the hit CW series entertains with an air-guitar concert!

Then, on tonight's episode, Debbie (Lori Loughlin), Harry (Rob Estes), Annie (Shenae Grimes), Dixon (Tristan Wilds) and Sean (guest star Josh Henderson) spend the evening playing games, and Annie overhears a phone call with Sean -- her alleged half-brother -- that raises suspicion.

Also, Adrianna (Jessica Lowndes) invites Brenda (Shannen Doherty) to attend a support day at her rehab center, but the day quickly turns upside down when Adrianna learns information that will cause her life to change forever. Brenda and Kelly (Jennie Garth) stand by Adrianna's side and Brenda reveals a secret she has been hiding from Kelly.

And finally, Dixon and Christina's (guest star Lauren London) friendship continues to grow when she invites him over to her house, an invitation he hides from Silver (Jessica Stroup).

"90210" airs at 8 p.m. on The CW.