Dr Robert Clark was a biologist and a member of Ernest Shackleton's Imperial Trans-Antarctic Expedition to cross Antarctica.
In 1915, the expedition's ship the Endurance was trapped in the ice. Clark was attacked by a whale whose DNA was altered by the Skith as part of their experiments. As a result of the morphic field being in flux, Clark's contact with the creature led to the field to start transforming him into a Skith. Following this, a group including some of Shackleton's crew, joined by the Tenth Doctor and Martha Jones, followed Clark to the Skith ship Oppressor One. The Skith imprisoned the group and prepared to study and dissect them, but after Shackleton got through to Clark, Clark released them. Martha brought most of the group apart from the Doctor and Shackleton back to the Endurance in the Doctor's TARDIS, before later coming back for them when they destroyed the Oppressor One. The destruction of the Oppressor One and the retreat of the Skith Mindcore to the Ownworld restored Clark to normal. After being brought back to the Endurance, Shackleton and fellow explorer Frank Wild came up with a plan to travel 250 miles west to Paulet Island, leaving the expedition abandoned. The Doctor mentioned that everyone on the expedition survived. (COMIC: The First)