Structurally, the season retread season 18’s formula of including a trilogy of stories bound together by an overarching theme. In this instance, the tripartite tale involved Turlough’s attempts to kill the Doctor at the behest of the Black Guardian.
20 - 1Arc of Infinity (1) Jan. 03, 1983
20 - 2Arc of Infinity (2) Jan. 05, 1983
20 - 3Arc of Infinity (3) Jan. 11, 1983
20 - 4Arc of Infinity (4) Jan. 12, 1983
20 - 5Snakedance (1) Jan. 18, 1983
20 - 6Snakedance (2) Jan. 19, 1983
20 - 7Snakedance (3) Jan. 25, 1983
20 - 8Snakedance (4) Jan. 26, 1983
20 - 9Mawdryn Undead (1) Feb. 01, 1983
20 - 10Mawdryn Undead (2) Feb. 02, 1983
20 - 11Mawdryn Undead (3) Feb. 08, 1983
20 - 12Mawdryn Undead (4) Feb. 09, 1983
20 - 13Terminus (1) Feb. 15, 1983
20 - 14Terminus (2) Feb. 16, 1983
20 - 15Terminus (3) Feb. 22, 1983
20 - 16Terminus (4) Feb. 23, 1983
20 - 17Enlightenment (1) Mar. 01, 1983
20 - 18Enlightenment (2) Mar. 02, 1983
20 - 19Enlightenment (3) Mar. 08, 1983
20 - 20Enlightenment (4) Mar. 09, 1983
20 - 21The King's Demons (1) Mar. 15, 1983
20 - 22The King's Demons (2) Mar. 16, 1983