Muslim pilgrims on the way to Mecca from a central African country find themselves being to sold into slavery.
When some of them protest, they are gunned down by the ship's captain. The orders are given by Sadik Bey (Charles Gray) over the radio in Rome.
His slave venture might be in trouble. A man called Dexter is flying over from America to testify to a UN committee. Ricco Poccari is due to meet Dexter but he has not checked in to his hotel.
A young woman Rosalina is also looking for Dexter. Unbeknownst to her, Sadik Bey, her boyfriend has abducted Dexter and torturing him to find out what he knows.
Poccari needs to break the gang up by using Inspector Rossi in a ruse.
Several characters mention that they find it hard to believe that the slave trade was still ongoing in the 1950s. I think there might be some truth to it. Pilgrims to Mecca from poorer countries were easy prey to a scammer.