Thomas turned to stare at Alexander and opened his mouth to tell him how wrong he was but the words would not come.
We could break it out, because too many subordinate clauses is always a pain to deal with.
Thomas turned to stare at Alexander. He opened his mouth to tell him how wrong he was, but the words would not come.
Still ugly. The problem is pronouns.
We know who he is staring at, right? Let's drop the 'Alexander so we can use him later instead of a pronoun.
Thomas turned to stare, opening his mouth to tell Alexander how wrong he was, but the words would not come.
Here, the target of his action (Alexander) gets double duty. By putting it in the middle, we know who he staring at and we dump two pronouns.