S1, E13: On their way to drive Karen home from the airport, Keith and Lucas collide with an oncoming vehicle, leaving Lucas unconscious and fighting for his life. At that moment, Dan is traveling to Deb's house to plead with her to give their marriage a chance, and he witnesses the accident. At the hospital, Dan must acknowledge that Lucas is his son in order to authorize emergency surgery. Karen is paged at the airport with the devastating news. Meanwhile, Peyton decides to tell best friend Brooke that she kissed Lucas.