In Dylan's Song, they leave America to go to Ireland to locate and extract a missing CIA operative. While they are gone, their CIA handler, Sam, agrees to watch over their angelfish business. Before they leave and unbeknownst to Sam, Dylan installs cameras so he can keep an eye on the angelfish while they're gone. Though he's a trained killer and a spy, he still has a very soft spot for his angels.
It turns out, he also has a soft spot for a border collie he'd left behind when he moved from Ireland to America. He'd found Shep a good home before he departed but they reunite in the book - and when Shep is mistaken for a CIA dog, he finds a way to get her to America so they can remain united.
