Who is the U.S. spy released from Cuba?

(CNN) - The release of American aid worker Alan Gross as part of the U.S. and Cuba's historic shift in diplomatic relations was nothing short of splashy.

We saw photos of Gross getting off a plane and being greeted by loved ones, as well as meeting with Secretary of State John Kerry. The freed American even held his own news conference.

And yet, very little is known about the details surrounding the other prisoner released from Cuba as part of this deal.

A U.S. intelligence agent who, up until now, very few people even knew existed.

CNN chief national security correspondent Jim Sciutto joins "The Lead" to discuss what we have learned about this agent.