It is night, and Roderigo attempts to kill Cassio. He misses, and Cassio wounds Roderigo. Iago appears, and wounds Cassio in the leg. Othello hears Cassio's screams and thinks that he has died, and so he goes to kill Desdemona. Iago kills Roderigo, and then fetches help for Cassio. Bianca arrives to be near her lover Cassio, and Iago attempts to blame his treachery on her.
Othello: Novel Summary: Act 5 Scene 1