The Flash Felicity Smoak (Emily Bett Rickards, right) from "Arrow" visits Barry (Grant Gustin, left) in episode 4 of "The Flash." Photo: The CW

Barry Allen (Grant Gustin) and the S.T.A.R. Labs team are taking out the bad guys one by one on “The Flash.” In episode 3 Barry stopped the Mist (Anthony Carrigan) from poisoning Joe (Jesse Martin) and the new superhero has caught the attention of a special guest star in episode 4. Plus, the synopsis for episode 4 reveals the next villain for the CW series.

According to the episode 4 synopsis, Barry will stop a bank robbery, but the perpetrator gets away after shooting a guard. The bandit, Leonard Snart (Wentworth Miller of “Prison Break”), later steals the “Cold Gun,” a weapon invented by Cisco (Carlos Valdes) that has the ability to kill the Flash. Barry must take Snart, dubbed “Captain Cold,” out before he strikes again.

Watch the promo for episode 4, “Gone Rogue,” below to see a preview of Captain Cold in action:

Barry will also get a visit from an old friend in episode 4. Felicity Smoak (Emily Bett Rickards) from “Arrow” stops by to check out the new hero’s powers after hearing about them from the Green Arrow (Stephen Amell). Felicity previously met Barry when he appeared in two episodes of “Arrow” in Season 2. The Green Arrow then appeared in “The Flash” premiere when Barry sought him out for advice. "The Flash"and "Arrow" will meet again in a crossover episode airing in November.

Meanwhile, episode 4 of “The Flash” will also see Joe giving Iris (Candice Patton) the silent treatment after finding out about her relationship with his partner (Rick Cosnett).

What will happen when Felicity visits Barry? Will she be able to help him take down Captain Cold? Fans will have to tune in next week to find out. “The Flash” airs on Tuesdays at 8 p.m. EDT on the CW.

Are you excited to see Felicity cross over to “The Flash” for an episode? Tweet your thoughts to @Ja9GarofaloTV.