Luke spends a lot of time looking at Bo, as a general rule (just like Bo spends a lot of time touching Luke, as a general rule). And in the first season, Luke has a more intense stare than he does later on, at least when looking at something he wants. So in this one, from The Big Heist, Bo gets around to noticing just how hard Luke looks at him.
Seems odd to start noticing things about Luke now, when he's only known the guy his whole life. It comes to him all the same, standing there at the same still site where they spent many a teenaged hour cooking, while Boss lays out the charges against them: the way Luke watches things.
Everyone looks at things, like the way Jesse's looking at them now. Half protective grizzly bear, half suspicious old uncle. Same kind of look he always used to get when Bo would show up two hours earlier than school got out, a note in his pocket about fighting and suspension, again. (Those fights were all Luke's fault, what with Vietnam being a dirty word at the time, and Bo having to defend his missing cousin's honor. Still it was hard to tan a hide that was half a world away, so Bo had taken the punishment for them both.)
Boss is looking at them too, righteous posture, but not really happy. Not yet, maybe he just needs to look at them from the other side of iron bars to achieve full out glee. Rosco's doing his share of looking at them, tough guy smirk topping off a body that's twitching like a four-year-old on Christmas morning. Enos is the only one not looking at them. He's a little too busy staring at his own feet.
Bo looks at things, just like everyone else. In fact it's looking that leads to him noticing things about Luke. Like how Luke doesn't look at things, he watches them. Right now, when Bo's trying to catch his eye to see how much trouble they're in and whether they should run for it, Luke's watching Boss. Studying on him, practically. Intense, blue-eyed scrutiny.
Which leads to the realization that makes Bo's stomach drop out from under him. Luke watches him, a lot. With those same blue eyes that don't miss a thing, that can see through swagger and past stances to the heart of a thing.
It's enough to suck the wind out of him, until Luke's smacking him on the back and, of course, watching him. Almost keeps Bo from breathing again, but then that blister on his foot twinges and he has to suck in air against the pain.
Winds up next to Luke in the back seat of Rosco's cruiser – again. Sits on top of him almost, not so much in worry this time as the half-focused thought that Luke can't see Bo all that clearly if he's that close. Stays snugged up tight to him in the jail, too, not to mention when they "confess" to Enos. (That time it's strictly practical. Luke needs to be watching the deputy for the right moment to make their move. He can't be sparing a single glance at Bo.) In fact, all the way through the "holdup" at the house until they enact Luke's plan to help Daisy's new beau, Bo stays as near to Luke's side as he can.
Somewhere in there they have to separate, but that's okay. Bo's wearing a ski mask by then, and Luke can't really study too hard on him. Besides, around that time, Luke's got to be watching Harvey Essex to assess whether the revenuer's going to turn on them and maybe just arrest him some Dukes, on principal.
But eventually the fun is over and they're back at home in their own living room. Luke's attention lingers on Neil Bishop for awhile, but it seems like he's no real threat to Daisy, so he doesn't bear watching.
Which puts those knowing blue eyes right back on Bo. Good Lord, Luke watches him. Heat creeps up Bo's neck, and he tries to cool it off by sipping at his beer. Doesn't seem to work, because in a second Daisy's teasing him about it. Everyone thinks it's cute: Bo's embarrassed about his mail-order boots. Everyone that's just looking, that is. Luke's watching, not laughing. Smirking, maybe. Could that be a wink?