I watched this episode again a few days ago and I was a bit bothered for the storyline. That being said, maybe this is more like a general nit-pick with series like this. In this episode we have a gentleman who follows the friend of Mac and later reveals that the woman he has been following is not what she seems to be. Doing this kind of plan seems very risky since we have established that the person working under diplomatic immunity is a quite ruthless man. Anyway, luckily he lets the gentleman live. After that the bad guys go to confront Mac and his friend on the houseboat. With bad luck they could have been killed, again.
I understand that Mac can predict human behaviour very well(like in this case) but for this plan to work, a lot has to go right.