A hand being held out for a handshake while another hand appears to move away

Last fall, a college junior I'll call Caleb received an offer for a summer internship with a midsize tech company. It wasn't his dream gig. But in an uncertain market for computer-engineering majors, it was better than nothing. So he accepted it. Then, hoping to land something better, he kept applying to more internships.

This spring, he got what he wanted: an internship that involved more interesting work, with a more established company, than the offer he had already accepted. But what to do about the first company, which was expecting him in a few months?