难道说 is a fixed rhetorical-question phrase that strengthens the tone of 难道. You use it at the start of a question to express strong disbelief, doubt, or surprise — equivalent to 'Do you really mean to say that…?' or 'Could it be that…?' in English. It often implies the speaker expects a negative answer or finds the situation hard to believe. Unlike 难道, 难道说 adds a slight conversational or narrative flavor, as if quoting or restating what someone might think.