Chase Through Time
Definitely my personal favorite episode.
WARNING-SPOILERS
What was most effective and even disturbing was the grim ending where Duval is left behind in the hive, about to be killed by the approaching (off-screen) giant bees.
I like the fact that we don't see the bees (I know, it was due to budget limitations) and it ends right before he is slaughtered in the most horrific way, but it played upon your paranoid imagination.
Also, the final moments reminded me of the dark ending of FIVE CAME BACK, where the criminal is left behind in the jungle, as the (off-screen) headhunters close in on him. I remember having disturbing nightmares afterwards. A shocking climax worthy of the EC Comics.
Also, I always wanted to see more of the Tic-Toc Installation, which I found intriguing, but the limited budget obviously prevented that.