Max barks at the park

On another walk with Max to clear his mind, John’s dog began barking furiously at a spot in the park.
‘What is it now, buddy?’ John asked, following Max’s lead. The dog’s frenzy was unmistakable, his barks persistent. John’s curiosity got the better of him.
‘Let’s see what you’ve found this time,’ he muttered. The spot Max was fixated on looked ordinary, but John knew Max’s instincts well.
This could lead to another crucial clue.