Along with Morka, K'to and several other Silurians, Okdel awoke in the 20th century. He had developed a relationship with the human Dr John Quinn. The Third Doctor convinced him that the Silurians could share Earth peacefully with mankind. When he realised that Morka was trying to wipe out humanity with a virus, he freed the Doctor and gave him the means to find an antidote.
Okdel was not named on-screen, only in the novelisation and in the novel The Scales of Injustice. The Scales of Injustice gives him the full name Okdel L'da. He was listed as "Old Silurian" in the credits.