139 Target Zylon part one

Zylons…the true scourage of the universe. In the 24th century, a great war is about to be decided. But the Doctor and Comdr. Triyad may find themselves on the opposite side of humanity. Ripples which play havoc with the time stream, a war machine ready to invade, and a weapon of unimagined power all speak of a final battle which will determine the fate of the galaxy for centuries…if the galaxy can survive. It will all be finished in 24 hours…one way or another…