For his sister, Benazir, who is still struggling to establish her authority after she became Prime Minister for the second time last month, Mr Bhutto's return is a severe embarrassment. He has already touched off a family feud, and may also divide the Pakistan People's Party (PPP), founded by his father, Zulfikar Ali Bhutto. Trading on the family name, the 39-year-old Murtaza won a provincial assembly seat in last month's election, although he failed to be elected to the national parliament.
Mr Bhutto fled Pakistan in 1977 after his father was deposed as Prime Minister. Two years later his father was executed, and Murtaza founded the Al-Zulfikar guerrilla group which carried out revenge attacks in his name, including the 1981 hijacking of a Pakistani airliner during which an army officer was killed.
Ms Bhutto, who took the path of constitutional opposition to the government, may have to choose between allowing her brother to go to prison and intervening to free him. The former course would widen the split with her mother, Nusrat, who was at Karachi airport to meet her son, and who accused Benazir's government of being 'worse than the martial law period' - a reference to the military government which executed her husband.
Refusal to show clemency to Murtaza also risks splitting the PPP between those, mainly from the family's ancestral province of Sindh, who see him as the natural male heir to his father's political legacy, and party members in other provinces who find the family feud a liability. Special treatment for him, however, would be a gift to the opposition.
Ms Bhutto had one political bonus yesterday. The former president, Ghulam Ishaq Khan, who dismissed her first government in 1990 for corruption and misrule, dropped out of the contest to become the next president, who will be chosen next week bylegislators. Other withdrawals yesterday left the Foreign Minister, Farooq Leghari, as the only PPP candidate.