Bruno Pontecorvo was a nuclear physicist. He was born in Pisa in 1913, went to University in Rome, and worked under Enrico Fermi. His research took him to Paris in the 1930's, where he met and married Marianne Nordblum (a Swede). Their first child Gil was born in Paris in 1938. With the fall of France, the young family crossed the Atlantic and entered the United States. By 1943 Bruno was employed by the United Kingdom on the British nuclear reactor programme at Chalk River in Canada. His children Tito and Antonio were born in Montreal in 1944 and 1945. Bruno came to work in the United Kingdom at the Atomic Energy Research Establishment at Harwell in 1948. In 1950 he was due to take up a teaching position at the University of Liverpool. The family disappeared in the summer, and it was eventually discovered that they had moved to the Soviet Union.