Barabas begins the play in his counting-house. Stripped of all he has for protesting the Governor of Malta's seizure of the wealth of the country's whole Jewish population to pay off the warring Turks, he develops a murderous streak by, with the help of his slave Ithamore, tricking the Governor's son and his friend into fighting over the affections of his daughter, Abigall. When they both die in a duel, he becomes further incensed when Abigall, horrified at what her father has done, runs away to become a Christian nun. In retribution, Barabas then goes on to poison her along with the whole of the nunnery, strangles an old friar (Barnadine) who tries to make him repent for his sins and then frames another friar (Jacomo) for the first friar's murder. After Ithamore falls in love with a prostitute who conspires with her criminal friend to blackmail and expose him (after Ithamore drunkenly tells them everything his master has done), Barabas poisons all three of them. When he is caught, he drinks "of poppy and cold mandrake juice" so that he will be left for dead, and then plots with the enemy Turks to besiege the city.