[The following article contains SPOILERS for Gotham: The Blade's Path.]

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Tonight's Gotham ended with a shocking twist - the return of one of the original characters who seemed to have left the city for good: Doctor Leslie Thompkins. The reveal came at the end of the episode, titled 'The Blade's Path', which saw Bruce Wayne (David Mazouz) finally kill Ra's al Ghul (Alexander Siddig) with the knife that everyone has been after this season. 'The Blade's Path' also focused on Penguin (Robin Lord Taylor) and his relationship with Sofia Falcone (Crystal Reed).

And as if all that wasn't enough, 'The Blade's Path' also saw the return of two of the show's longest-standing characters. Butch Gilzean (Drew Powell), has returned from the dead as Solomon Grundy (with his hand back in place but his mind very much missing), who is now teaming up with the Riddler (Cory Michael Smith). In addition, the final moments of the episode brought back Dr. Leslie Thompkins (Morena Baccarin), who we last saw alive, but leaving Gotham city.

Related: Gotham Reveals First Look at Solomon Grundy

The reveal is only a few seconds long, and is the very last scene of the episode. Riddler and Butch/Solomon are headed to an underground boxing ring to fund their strange new partnership, and are sent to see the doctor before Butch can compete. The scene cuts to a beaten man being tossed on the table, and a lackey calling out that the boss wants the Doctor to take a look at the new guy. A voice replies that she'll be right there, before we see the back of the Doctor's head as she swigs from a bottle of liquor. Finally, the Doctor turns, revealing Leslie Thompkins.

Leslie Thompkins returns to Gotham season 4

Leslie has had a tough time of it in Gotham City so far. In the earliest seasons, she fell in love with Jim Gordon (Ben McKenzie), but was tormented by his ex, Barbara (Erin Richards) who was going completely crazy. Leslie and Jim had some good times, but their relationship ended when Leslie became pregnant, and left Gotham to start a new life somewhere less dangerous. Jim eventually tried to find her, but discovered her with a new man. Last season, Leslie returned with her new fiance, Mario (James Carpinello), and seemed to be doing well again (although she had lost the baby). However, Mario ended up infected with the Tetch virus, and Jim Gordon shot and killed him. Leslie then intentionally infected herself with the virus, turned into Dark-Leslie, and tormented Jim for a while, before she was cured and left the city a second time.

Now she's back, and while Leslie has been cured, she still looks a lot like Dark Leslie did - and has fallen a long way from her early days as a sweet and scrubbed medical examiner. It seems that she's been hiding out in Gotham's underground scene, putting her skills to use as a doctor for the boxers, and putting her demons to rest by hitting the bottle. Although she is not in contact with Jim, it's likely that she is still a little bit obsessed with him, so these two are bound to meet once more. She may end up bumping into Barbara, who also returned this season (after being killed), and that is sure to be a fascinating meeting, given the history between the two. We'll have to wait and see what new horrors Gotham has in store for poor Leslie, but it's sure to be interesting.

Next: Gotham: Ivy Will Gain Poison Ivy Powers in Season 4

Gotham continues next Thursday with ‘A Dark Knight: Hog Day Afternoon’ @8pm on FOX.