Harold Pinter's 1978 drama Betrayal and William Shakespeare's 1598 comedy Much Ado About Nothing would seem at first glance not to have very much in common, and this is generally true. Although Much Ado About Nothing is a comedy, there are certain serious aspects of the play that relate to Betrayal.
The plays share common themes of love, betrayal, communication (or lack thereof), and the nature of relationships. Both plays also explore the characters' seeming inability to know themselves and those around them.
The focus in Betrayal is on a love triangle involving a married couple, Robert and Emma, and Emma's affair with Robert's best friend, Jerry, who is married to Judith (who doesn't actually appear in the play).
In Much Ado About Nothing there's a dual focus on the relationships between Beatrice and Benedick and between Claudio and Hero. Both plays explore the changing nature of these relationships and the interactions of the characters involved in those relationships.
Emma had an affair with Jerry for seven years during the time that she was married to Robert. Robert learned about the affair four years after it began, but Emma didn't tell Jerry that Robert knew about the affair and continued the affair with Jerry for two more years before breaking up with him.
In time, the marriage between Emma and Robert comes to an end. Robert confesses to Emma that he's had multiple affairs during their marriage.
Emma finally tells Jerry that Robert knew about the affair, but she tells him that she told him only the night before, not years ago.
The betrayals in Betrayal are obvious. Emma and Jerry betrayed Robert. Jerry betrayed his wife, Judith. Emma betrayed Jerry, first by not telling him that Robert knew about their affair, then by lying to him about when Robert found out about their affair. Robert betrayed Emma with multiple affairs.
There are no such multiple betrayals in Much Ado About Nothing, but the evil Don John, who wants to marry Hero, tells Claudio that Hero has been unfaithful to him with Borachio. Believing that he's been betrayed after seeing Borachio enter Hero's bedroom, Claudio waits until their wedding day to expose Hero's supposed affair with Borachio.
Claudio betrayed Hero by abandoning her at the altar. Claudio also betrayed Hero by not trusting her and by failing to communicate with her honestly about her supposed affair with Borachio.
Communication is also a central issue in Beatrice and Benedick's relationship. They just can't seem to communicate effectively with each other, which leads to misunderstandings, which leads to arguments, which leads to swearing off love forever. It takes the intervention of other characters to finally get Beatrice and Benedick to actually communicate with each other and to be able to express their love for one another.
Much Ado About Nothing ends happily with multiple marriages, as frequently happens in Shakespeare's comedies. Betrayal ends unhappily, with no relationships intact.