What change does Kit notice in John Holbrooke when he comes to dinner with Rev. Bulkeley?

Kit notices the way John looks at Judith.

When the prayer was ended, the thanks repeated and the goodnights said, Rachel saw her guests to the door. She held out her hand to John Holbrook.
"I hope you will come again," she said kindly. "We would like you to feel welcome in our house."
John looked back to where Judith stood behind Mercy's chair. "Thank you, ma'am," he answered. "If I may, I would be very happy to come again."