New details have been revealed about Severide's (Taylor Kinney) car accident in the upcoming episode of "Chicago Fire."

NBC will welcome January with a two-hour crossover between its two "Chicago" series. The firefighters and the police officers will unite in a thrilling investigation involving Severide. A new sneak peek (according to Yahoo News) shows more details on the night that the lieutenant will allegedly be involved in a terrible accident. In the clip, the members of Truck Co. 81 are shown hurrying to respond to a call about a highway mishap. When they get there, Herrmann (David Eigenberg) immediately recognizes Severide's car. It was empty though, and no matter where they look, they cannot find him. The onlookers also have nothing to say about what happened to the driver of one of the cars.

Meanwhile, the mystery of Severide's whereabouts was revealed in a promo released previously. In the other teaser, he is shown sleeping on the sofa at his apartment. Voight (Jason Beghe) and Lindsay (Sophia Bush) of "Chicago P.D." knock on his door and tell him he is being investigated for an accident. Severide cannot remember anything, though. He also cannot explain why he has a nasty gash on his forehead. Voight then informs him that one of the people in the other car just died. Severide is now facing a vehicular manslaughter case.

Nothing seems to be going right for the lieutenant these past few episodes. He told Casey (Jesse Spencer) that he felt dead inside. Severide is supposed to be donating his bone marrow to a patient in the upcoming episodes. With him in danger of going to jail, will he still be able to keep his promise to the sick woman? There must be a reason why Severide cannot remember the accident.

"Chicago Fire" season 5 returns Tuesday, Jan. 3, 2017 at 9 p.m. EST on NBC.