Batman gets hit with a love spell during battle that knocks him out and will make him fall in love with the first person he sees when he wakes up. The league takes him back to the tower and while they wait for Zatanna or Dr Fate to come help break the spell they all agree Superman should be who Batman sees and he can deal with a lovestruck Batman. Only, when Bruce wakes up and sees Superman, he doesn't act any differently. He just gets up and demands a mission report and tries to go about business as usual, much to everyone's confusion (and to the disappointment of Hal, who had his phone out ready to record). They explain the love spell and wonder why nothing happened and Bruce just says that obviously it didn't work and to not worry too much about it.
The spell did work it's just that Bruce was already in love with Superman so nothing actually changed outwardly. Zatanna gets there a few days later and examines him, and is also confused bc there's definitely a love spell on him and there's no reason it shouldn't be working. To prevent her from looking further into it and making a big deal, Bruce, in private, hints at why there might not be any effects. Zatanna gets it and agrees to remove the spell and say that it just wasn't that strong after all.
Everybody seems to accept that explanation and move on, except for Clark, who knows his best friends is hiding something and he's determined to find out what.