Spoiler Level: High
Data picks up a radio signal asking if anyone is out there, and answers it. What spirals from there gets the crew of the Enterprise deeper and deeper into bending the Prime Directive. Kirk would be proud.
One has to question Data's judgment through most of the episode. His decisions, while logical for showing compassion for another living being, seem a little rash for a Starfleet officer-- especially one without emotions.
Like the rest of the season it's a strong character episode, and not just for Data. Wesley gets a fair amount of time in the spotlight when he's given command of a survey team, and everyone else gets to have good scenes as he comes to them all for advice. And probably the best character scene in the episode is when Pulaski dares to imply that Worf's black-and-white reading of the Prime Directive is cowardly, and Picard rushes in to do damage control!
This is also one of those episodes that pretty much set the status quo for the Berman era of Star Trek. Debating the Prime Directive from so many different angles makes for great Trek-- when it was new. But once they laid down their guidelines in episodes like this, it made it much more cut-and-dry on future Trek shows. (Which was part of why I was so looking forward to Star Trek: Enterprise-- no Prime Directive! Then they go and screw it up with having the Vulcan's already having their own non-interference policy. But never mind that, I'll save that rant for when I eventually get to "The Communicator.") But for this point in Trek history, getting to dissect the Prime Directive made for some great drama.