S1·E20 A Dream of Jennifer

Buck is haunted by the appearance of a young woman who bears a striking resemblance to Jennifer, a woman who Buck left behind when he was propelled into the 25th Century. He follows her, finds out her name is Leila Markeson, and soon discovers that she was made to look like Jennifer in order to lure Buck into a trap set by an alien who wants Buck to stop a space freighter from delivering weapons to a planet his people hope to conquer. Buck gets Wilma to detonate a warhead to deceive the aliens into thinking the shipment is destroyed. Buck defeats the enemy, but loses Leila, and his lost love again, as she tearfully dies in his arms.