Having been cut off from the TARDIS when the facility where he had landed, the DEEP, was lost and presumed destroyed, the Doctor remained on Earth acting as a surrogate father to Ruth Mills, the daughter of Eric Vollmer, who was lost when the DEEP was destroyed. When the DEEP was rediscovered, the Doctor attempted to recover his TARDIS, but when Ruth followed and learned that the Doctor had killed her father on the chance that he might continue the dangerous work being carried out there, she simply stood by as the DEEP's sole survivor broke the Doctor's neck, noting that she would remain and watch the Doctor regenerate as many times as she had to in order to he was finally dead. (NOTVALID: Full Fathom Five)