Antonio and shylock are discussing the payment options for Bassanio. If Antonio doesn't give money back to shylock in 3 months then shylock gets to cut off a pound of flesh off of Antonio of shylocks choosing. Antonio is heavily relying on his ships to make it back.
Ay, sir, for three months.
Three thousand ducats, well.
For three months, well.
The Prince of Morocco chooses the golden casket. He fails to choose the right one, thus receiving a scroll inside a skull saying he chose wrong. Portia tells him to leave.
Shylock takes Antonio to jail after finding out he is bankrupt. Antonio begs for Shylock to answer but shylock only sees him for a Christian. Assured that the duke will grant him justice, Shylock insists that he will have his bond and tells the jailer not to bother speaking to him of mercy.
Portia enters, disguised as Balthasar. The duke greets her and asks whether she is familiar with the circumstances of the case. Portia answers that she knows the case well, and the duke calls Shylock and Antonio before her. Portia asks Antonio if he admits to owing Shylock money. When Antonio answers yes, Portia concludes that the Jew must be merciful. She also brings up that if shylock were to shed any christian blood that he would to give his money away.
Portia explains to Bassanio that she was disguised as Balthasar to help Antonio and win the case against Shylock. She also admits to tricking him into giving him the ring he promised to never give up until his death. However Portia somehow forgives him and the story ends in a happy ending.