Secret of the Unicorn is an episode from ThunderCats Roar, which originally aired on March 7, 2020.
Official Summary[]
A crying unicorn appears at the Cats' Lair and weepily tells the ThunderCats that all of her unicorn friends have been captured! Tygra thinks he's just the unicorn expert to help the last of the unicorns, he just needs her to stop sobbing long enough to tell him who took her friends. Easier said than done.