'Chicago P.D.' season 4 spoilers: crossover with 'Chicago Fire' sees Lindsay and Severide run-in

A promotional still from "Chicago Fire" season 5, episode 8, "One Hundred" | Parrish Lewis/NBC

A new sneak peek of the "Chicago Fire" and "Chicago P.D." crossover next year has been revealed and it teases a mega awkward reunion.

As revealed before, Severide (Taylor Kinney) will be part of a crossover event between the two shows. It turns out that he will run into his old flame Lindsay (Sophia Bush) in this episode.

Both in shock, they engaged in an awkward small talk that led to Lindsay inviting her ex to take his new girlfriend, Stella (Miranda Rae Mayo), on a double date with her and Jay (Jesse Lee Soffer).

Before this, Severide pushes for a bone marrow procedure to save the life of Anna (Charlotte Sullivan), but things do not go as he expects, leading him to return to his old habits.

It turns out that this double date will not be the final encounter of the two in the "Chicago Fire" and "Chicago P.D." as it appears that Severide will seek Lindsay's help with a hit-and-run problem.

Severide will be brought for questioning after it was discovered that his car has caused a crash. It is believed that he will ask Lindsay to prove his innocence as it was revealed a group of carjackers are the perpetrators.

According to Entertainment Weekly, this case will bring "complicated feelings" from both Lindsay and Severide. It remains to be seen where this will lead them.

As she deals with this in the "Chicago Fire" and "Chicago P.D." crossover, Lindsay will also deal with a family issue involving meeting her estranged father fresh from prison.

The crossover will also follow up on Casey (Jesse Spencer) and Dawson's (Monica Raymund) fight to co-adopt Louie, whose birth father arrives just as they get closer to being Louie's legal parents.

The "Chicago Fire" "Chicago P.D." crossover will air on Tuesday, Jan. 3, from 9 to 11 p.m. ET on NBC.