When most people think about Much Ado about Nothing, they think about Beatrice and Benedict, the two sparring couples because that is the more fun plot. Sure, there’s Claudio and Hero in there somewhere, but the reason it is so beloved is because of the sparring lovers and because of the efforts of the other characters to get them together. But Claudio and Hero, while being much more traditional lovers, have much more impact on the plot and on the other characters.
When Claudio and Hero first meet, in Act 1, Claudio whispers to Benedict, “Didst thou note the daughter of Signor Leonato?” Claudio is instantly smitten. He immediately tries to win her heart. He and Don Pedro, Claudio’s superior, have a conversation about Hero; where upon Don Pedro decides to woo Hero on Claudio’s behalf. Then Don Jon enters the picture. The clear villain of the piece, as soon as he hears of Don Pedro’s plan to woo Hero for Claudio, he says, “[I]f I can cross him [Claudio] in any way, I bless myself every day.”
Later at the masquerade ball, while Don Pedro is wooing Hero like he told Claudio he would do, Don Jon goes to Claudio and plants seeds of doubt in his mind. Note how this foreshadows the major reveal later in the play: Claudio doubts Hero’s love. After Don Jon plants seeds of mistrust, Claudio nearly challenges Don Pedro, but before he can do it, Don Pedro announces to him that he successfully won her hand for him, Claudio. The couple happily plan for their wedding.
Don Jon, still steaming that his former plan was ruined, then plans an even more elaborate scheme to undo the couple: Borachio, a friend of his will make love to Margaret while shouting Hero’s name. Then he comes to the group of men and tells them that Hero has been unfaithful. Claudio doesn't believe it at first, but is persuaded to investigate.
The next day, an obviously bitter Claudio shows up at the wedding and accuses Hero of cheating on her the night before the wedding. Hero tearfully denies it but Claudio is insistent, refuses to go through with the wedding and storms out, making Don Pedro shocked and displeased at the woman who supposedly dishonored Claudio. Her father Leonato also furious, says, “let her die.” But Friar Francis stops Hero’s father and tells them that he believes she is innocent, and quizzes Hero to show that she was wronged. Then they hatch a plan: they will all say Hero is dead, will make Claudio remorseful and bring out the truth.
Meanwhile, the local watch overhears Borachio and his friend Conrade discussing the evil plan, and is brought before a judge, where he confesses their part in the plan. Claudio, who by now believes that Hero is dead, agrees with Leonato to marry another of his daughters who is “almost the exact copy of my child that’s dead.” Claudio, by now remorseful, agrees. At the wedding, the woman is masked and Claudio asks to see her face. She is revealed to be Hero and after Claudio gets over the initial shock of seeing her alive, agrees to wed her and they live happily with the other couple, Beatrice and Benedict.
What’s interesting about Hero and Claudio’s relationship is how the seeds of mistrust that Don Jon plants near the beginning of the play foreshadow how Claudio is ultimately undone. Claudio sees what he thinks is Hero in the arms of another man and is heartbroken and angry, twice. The second time is right before their wedding day. Shakespeare weaved the hint about what’s to come subtly enough by distracting the audience with the sparring of Beatrice and Benedict. When the reveal of Hero’s supposed treachery comes out, it seems to come out of nowhere, out of left field. But the master playwright he is, he weaves the Don Jon plot so that anyone following the play in earnest can spot the writing on the wall.