Tal vez + indicative
In the book "La ciudad de las bestias" I came across this sentence: "Tal vez el peligro de la enfermedad de Lisa te ofrece una oportunidad extraordinaria." I had been told that words/phrases like "tal vez", "quizá", or "es posible" are followed by the subjunctive when they are used, because they add an element of doubt. However, in this sentence, the indicative is used. Is this because the speaker is pretty sure that it will offer a good opportunity? Or is there another reason?
Thanks in advance
3 Answers
Brady is right (smiley) Spanish in a nutshell

It seems this operates in pretty much the same way that "si" clauses work. Uncertainty is implied, but using the subjunctive depends on whether the uncertainty is "probable" or "unprobable". Here is a link to a good thread on the subject tal vez subjunctive
Both can be used, depending on the amount of doubt that you want to express.