Investigation Held by ZnaToKi / Season 1 Season guide Investigation Held by ZnaToKi: Season 1 23 episodes Premiered Feb 14, 1971 Updated Jul 23, 2026 Spoiler-safe Advertisement Episodes S1·E1 Episode 1 Feb 14, 1971 · 55 min S1·E2 Episode 2 Apr 18, 1971 · 55 min S1·E3 Episode 3 Nov 9, 1971 · 55 min S1·E4 Episode 4 Feb 8, 1972 · 55 min S1·E5 Episode 5 May 29, 1972 · 55 min S1·E6 Episode 6 Sep 16, 1972 · 55 min S1·E7 Episode 7 Nov 11, 1972 · 55 min S1·E8 Episode 8 Sep 1, 1973 · 55 min S1·E9 Episode 9 Nov 10, 1973 · 55 min S1·E10 Episode 10 Aug 26, 1975 · 55 min S1·E11 Episode 11 Jun 4, 1977 · 55 min S1·E12 Episode 12 May 20, 1978 · 55 min S1·E13 Episode 13 Nov 11, 1978 · 55 min S1·E14 Episode 14 Oct 19, 1979 · 55 min S1·E15 Episode 15 Nov 9, 1980 · 55 min S1·E16 Episode 16 Nov 14, 1981 · 55 min S1·E17 Episode 17 Nov 9, 1984 · 55 min S1·E18 Episode 18 Mar 23, 1985 · 55 min S1·E19 Episode 19 Dec 27, 1985 · 55 min S1·E20 Episode 20 Apr 11, 1987 · 55 min S1·E21 Episode 21 May 21, 1988 · 55 min S1·E22 Episode 22 Nov 11, 1989 · 55 min S1·E100 Episode 100