The O.C. - Season 4

Marissa is gone but not forgotten. Definitely not forgotten: Julie has hired a detective to find Volchok, who caused Marissa's death... and she wants to make sure the P.I.'s report ends up in the hands of angry Ryan.

South of the border... Ryan slips away to Mexico to search for Volchok. Seth rides shotgun. And worried parents Sandy and Kirsten soon follow. Meanwhile, Summer has a surprise dorm visitor at Brown.

Julie is no longer invited. But guess who is coming to dinner: Homeless men, recruited by Summer, show up for the Cohen Thanksgiving. Ryan will be there, too - if he doesn't first commit murder when he learns where Volchok is.

Great news, Seth: The real artificial Summer is back! Her eco-activism is just a way of coping with Marissa's death. Or is it? Ryan isn't ready to be Ryan the Rescuer again. But Taylor needs rescuing.

Taylor is sure the remedy for Ryan's sleeplessness is... Taylor! Plus: Summer is set up to take the fall for lawbreaking activism at Brown. And Kaitlin and Julie eye the same himbo.

Love is a funny thing: Che handcuffs himself to the newly expelled Summer. And a sexy thing: Ryan fantasizes about Taylor. And a tender thing: Sandy and Kirsten share a recommitment ceremony.

Sandy is married to Julie. Kirsten is Mrs. Jimmy Cooper. Summer is engaged to Winchester. Seth is in full geek mode. It's a parallel Newport. And Ryan, stuck there after a conk to the head, must change it.

Seth is clueless about what to do for New Year's Eve. Solution? Crash the Ryan-Taylor road trip to Vegas. Now add pregnancy tests, a space-alien rave, thefts, misunderstandings, pursuits and a marriage proposal and it's time to welcome 2007!

Warm hearts, cold feet: Seth and Summer each look for a way to call off the wedding. Who will crack first? Ryan's biological father plays the Big-C card in hopes his son will see him.

Taylor's ex-hubby writes a hot-selling erotic novel. Who's the lead character? Three guesses and the first two don't count. Seth seeks Dr. Roberts' permission to marry Summer. Kirsten uncovers Julie's biz scam.

Take her, I want her. Ryan overcomes his indecision and competes with Henri-Michel for Taylor's affections. Che leads Seth on a trek of spiritual renewal. Embrace your inner otter, Seth!

Free Newport Chuck! Che - with more than activism on his mind - enlists Seth in a plan to spring a groundhog from it's Feb. 2 rites. Kirsten has a 40th-birthday party... and reveals another reason to celebrate.

Julie and Gordon? Or Julie and Frank? Summer and Seth? Or Summer and George? No, make that GEORGE. Mysteries of the heart (and the meddling of others) unfold as Valentine's Day nears.

Make a movie: Summer challenges Seth's passivity. Make a move: Taylor wants to hear Ryan's profession of love. Make a mess of it: Kaitlin floats rumors about Frank and clown porn. Make way for Mother Nature... everyone!

Everything's okay. As okay as anything can be after a major earthquake. Now come coping, staying calm, helping... and somehow getting Ryan to the hospital before he bleeds to death.

Six months after Mother Nature grabbed everyone by the neck and shook, events return to normal. Very normal. But complacency is never the Cohen or Cooper way. Time to follow the head and heart to what's right.