Season 2 pairs up Four with the Unsexy Romana and K9, set after the events of The Key to Time-Wasting but before the regeneration into Sexy Romana. There undoubtedly would've been more stories set in this time period, but Mary Tamm died before any of Season 2 was even officially released. Le sigh. Season 8 is set for release in 2019 and will feature Four pared up with a new companion, Laan Kelso.