Up til now, what we've seen is Mick's attention solely on Beth. He's saved her a bunch of times, they've done a few cases together. Ignore for the moment Beth's got Josh - we've discovered Beth knows who saved her when she was little and you KNOW she's developing feelings for Mick (I don't know about y'all, but I don't go around sniffing the shirts of guys I hate).
Enter Morgan, who's a dead ringer for Coraline. Mick's already given Beth the "intense affair" talk, so we know this woman reminds him of Coraline (WE know she's Coraline, but THEY don't know it yet). Mick's attention is diverted.
Perfectly natural human response, I'm thinkin.
