The Time Tunnel - Season 1 Episode 11 Secret Weapon

Doug and Tony arrive in Russia in 1956. The Tunnel staff try to contact them with F-5 probes, which prove highly dangerous. In the last probe the team sends a message telling the guys to contact ""Alexis"", pose as defecting scientists, and find out about Project A-13. In the present-day, General Parker is dealing with a scientist named Biraki and wants to know what his connection is. The guys are lead to the project in 1956, where Biraki is working on a Time Tunnel for the Russians under the supervision of Hruda. Doug determines the project is doomed to fail, and they try to escape and are recaptured. They also find out that Alexis is a double-agent. With some help from the Tunnel team, the guys manage to survive the probe, then sabotage Biraki's project in the past. The Tick-Tock staff witness the whole thing and tell Parker that Biraki is trying to get revenge for the destruciton of his Tunnel in '56, then manage to transfer Doug and Tony to another time period after they escape.