'The Flash' season 2 spoilers: Mark Hamill returns, relationships are shaken

CW

"The Flash" season 2 episode 9, titled "Running to Stand Still," will serve as the series' midseason finale, and according to a report from Collider it will bring back Mark Hamill as the Trickster while also shaking up several of the core relationships in the show.

The Flash - Trickster, Captain Cold and Weather WizardCW

The Trickster will be joined by Captain Cold (Wentworth Miller) and Weather Wizard (Liam McIntyre). Images from the report showcase the three may be joining forces for a major heist that will occur during the Christmas celebration, but given that Captain Cold is set to be a member of the "Legends of Tomorrow," he may back out of this plan.

It is also shown that Caitlin Snow (Danielle Panabaker) will be spending more time with Earth-2's Jay Garrick (Teddy Sears), implying that this episode will kick off a romantic relationship between the two. The two started getting intimate in previous episodes but the images here reveal they might make their relationship official.

The Flash - Patty and BarryCW

Other images showcase Barry Allen aka The Flash (Grant Gustin) with his new girlfriend, officer Patty Spivot (Shantel VanSanten) and it is hinted she may now be aware of his secret identity. As of the time being, Patty is the only person in the main crew who is unaware of The Flash's identity.

Most surprising, however, is the image showcasing the arrival of Wally West (Keiynan Lonsdale). At this point on the show only Iris (Candice Patton) is aware she has a brother while her father Joe (Jesse L. Martin) has been kept in the dark about it. Fans of the comics will recognize Wally West as the next person to inherit the role of the Flash.

It is uncertain if Wally West will gain his super powers and connection to the Speed Force in season 2 or if he is merely being introduced with a possibility of him joining the heroes in a later season. His arrival, however, is expected to shake up Joe and Iris' life as neither knew about Wally's existence until Iris' mother returned to Central City.

"The Flash" season 2 episode 9 will air this Dec. 8.