The link between the two stories arises as a result of the relationship that Bassanio has with characters in the two plot streams. The association is created when Bassanio, who is out of pocket, approaches his friend and confidante, Antonio, a wealthy Christian merchant, for financial assistance so that he may woo the beautiful Portia, a wealthy heiress from Belmont. Bassanio wishes to stand an equal chance against a number of other suitors, who come from privileged backgrounds and the money will give him such an opportunity.
Antonio does not have the ready cash that Bassanio needs but asks him to seek a loan in Venice by using his name as guarantee. He is a person of good standing and assures Bassanio that he will also seek a loan. Bassanio soon encounters Shylock, the Jewish moneylender, who is prepared to extend him a loan of 3 000 ducats should Antonio sign as surety to the bond.
Antonio agrees to Shylock's harsh terms which state that the loan should be settled in three months without any interest charged. If he should forfeit, Antonio has to allow Shylock to cut out a pound of his flesh. Bassanio asks his friend not to agree to these terms but Antonio, confident that he will be able to settle the debt comfortably, signs the agreement.
Bassanio takes the money and goes off to try his luck in winning Portia's hand in a lottery, in which a suitor should choose the right casket from three, that her deceased father had concocted. It is through these actions that an association between the two stories is created.
It is important to note that Antonio and Shylock despise each other. Antonio believes that Shylock is committing a grave sin by lending out money and profiting from the interest he charges. Shylock hates Antonio for having severely criticized him openly and humiliating him by spitting on his gaberdine, kicking him and calling him a dog. He seeks revenge against the Christian.
Bassanio is successful in choosing the right casket and wins Portia's hand. He does, however, receive an unsettling message from Antonio in which he states that he has been imprisoned for forfeiting on the bond. He had suffered a number of mishaps with his ships and could not settle the debt. The vengeful Shylock has been insistent that he should have his pound of flesh.
Bassanio is utterly distraught. Portia notices his distress and after discovering the reason for this, offers to help. She urges Bassanio to rush to his friend's aid immediately after their marriage and offers to repay the debt many times over. She formulates a plan to further assist the traumatized Antonio by going to Venice disguised as a doctor of law with Nerissa as her assistant. It is in this manner that the two plots achieve a confluence.