A secret, high-technology international agency called SHADO defends Earth from alien invaders.

Intellectually driven doctoral student Rosamund Stacey, while undertaking graduate work at the British Museum, becomes pregnant after a brief affair with a television newsreader. Against the advice of her best friend, Lydia, Rosamund chooses to keep the baby and adjusts her life to include both her studies and her pregnancy. However, when the baby is born, an unforeseen complication threatens the self-sufficient life Rosamund plans for herself.