Some Lapse of Time - S1.E10

Dr Max Harrow is awakened from a re-current nightmare in which he is pursued by a barbaric accusing figures, to find collapsed on his doorstep, The tramp is suffering from a genetic radiation disorder that should killed him in infancy as it did Harrow's baby son. The ma is the living image of Harrow's nightmare figures, Clutched in his hand is a human finger bone and he speaks a strange, unknown tongue, Why did he collapse outside Harrow's house? What is his motive for tracing him?.