The most-watched series in the history of Investigation Discovery, “On the Case With Paula Zahn,” has received a second-season renewal from the cabler.The newsmagazine, whose murder and mystery investigations are highlighted by field interviews by former ABC, CBS, CNN and Fox anchor Zahn, will return with 13 episodes in the spring. The series’ initial 13-episode order runs through mid-January. “On the Case” premiered Oct. 18 to record numbers for an ID series debut and achieved an all-time ID high with its Nov. 15 airing. Airing at 10 p.m. Sundays, the program averages about 400,000 viewers per episode. Scott Sternberg and Scott Weinberger exec produce the series with Zahn.