A shift in the atmosphere Ms. Petrova’s return flight from Paris landed in Boston on the evening of Feb. 16. As the plane sat on the tarmac, she texted back and forth with Dr. Peshkin, trying to confirm how she…

A shift in the atmosphere Ms. Petrova’s return flight from Paris landed in Boston on the evening of Feb. 16. As the plane sat on the tarmac, she texted back and forth with Dr. Peshkin, trying to confirm how she…