It could have been a 4 if our H hadn't been so bloody determined to send the h on her way "for her own good". Since he's a spy, and she, unknowingly, is the daughter of an Irish terrorist (who died when she was a tot, ostensibly by drowning but actually attempting to plant a bomb) who had another daughter who is now a fanatic...and wants her dead just because she exists... yeah, you can see how well this works. He almost succeeded once but called her for some inexplicable reason which prompted her to try to hunt him down. She didn't know he was a spy (he was undercover) so got the shock of her life to find out there actually was a person by that name but it wasn't him...and she got angry and started looking for him.
There's a lot of book packed in this, and some other things bothered me too - her lack of subtlety, her strange determination to help the Irish cause. Yes her sperm donor was Irish, but she was American. Her being independently wealthy yet having cousins who were hillbillies. And for some reason, she was sure he was lying yet it never occurred to her that maybe he was lying about everything.