This was the best of the recent episodes in my mind. I didn't see it the first time it was broadcast as our power was out so I recorded it during a repeat showing and finally watched it last night. Boy am I glad I did. It was a non-stop excitement ride. It dealt with Zoe's and Jo's relationship with Zane as well which added to the overall tone.
While Jo is going to pick up Zoe from the airport we come in on everyone getting suspicious of how oddly Allison is reacting. Carter becomes very suspicious and starts to investigate what happened previously when Allison was in a wreck. Henry, Carter, and Zane break into the medical records computer and find a remote control interface has been implanted in her brain. She is actually be controlled by an old Eureka employee, Beverly Barlowe, who is attempting to steal all of Eureka's secret project data. Allison has just taken over Eureka again as Fargo is preparing for the Titan mission. Once she has resumed control Beverly starts preparing for the theft.
When Carter and the others discover what is going on Beverly implements a backup plan which knocks out everyone in Eureka that has taken the inoculation to protect them from causing any sickness with the Titan crew. The inoculation actually implanted nano-bots in them which knocks them all out when activated. Meanwhile Jo and Zoe return to town to see everyone unconscious in Eureka. Jo never took the inoculation and of course Zoe hadn't either.
They start investigating and find Carter unconscious in his office. They take him to the medical center so Zoe can try and figure out what is going on. Also they see a helicopter coming into Eureka that they realize is involved in the mystery. It carries two accomplices to assist Beverly. While Zoe works on Carter Jo heads off to find Allison, Beverly actually, without really knowing she is involved. Jo is stunned and placed in her holding cell. Zoe now has figured out that Allison/Bev is up to no good and tries to figure out how to take care of her.
Bev's two goons take off after Zoe while Bev continues to work to steal the Eureka data. Zoe knocks out the first goon and Bev starts locking down level 3 but Zoe escapes. The other goon looks for her in the lobby where Zoe is faking being unconscious and when she thinks he is gone she gets up only to find him still there. She zaps him with the stun gun and then finds Jo who she releases. Jo attempts a break in to the computer systems which alerts the built in security systems and a total system lock out starts preventing Bev from transmitting the data out. Bev decides to steal the data storage hardware instead and takes it to meet her goons aboard the helicopter. Zoe meanwhile has been attempting to resuscitate Carter and becomes scared her attempt is actually going to kill him. She tries a second method of resuscitation that works.
Jo though is out after Bev and catches her attempting to board the helicopter. She confronts her and when Bev continues to the helicopter she shoots her with her stun rifle saving the data from being stolen. Carter has since recovered and they start to resuscitate the entire Eureka population.
This was a non-stop fun ride episode which involved everyone and made for a great return visit by Zoe. The only thing is I don't think the follow up episode really explained much else about Zoe or Bev leaving that dangling a bit in the air. I gave this one a 9.5.