She Was Cheating On Him
He learned that his wife was hiding from him a double life. Fair enough, someone in her shoes would’ve gotten lonely. This was not, however, an excuse to betray his trust. She was pretty good at hiding secrets, but Thomas wasn’t going to lie down.
Unable To Forgive Her
As you can imagine, Thomas was stunned by the treachery. He couldn’t even forgive Iris for what she did. He opted to apply for divorce instead. However, none of this was easy for him. We can understand fully that after the discovery he was really sad.