I am fully agree with Uly. May be your sentence looks like (Полностью согласен с Ули. Может быть, ваше предложение выглядит):

Let's suggest the only one betrayed.

Then the translation should be (Тогда, перевод):
Давайте предложим, что только один предавал (был предателем).

Maksim, that would be: "Let's suggest that only one was betrayed." I have turned her "sentence" many times, and can't make any sense of it. I don't even know what to add to it to make it understandable.