Now Preston was flushed. “I would keep him at an arm’s length. Don’t be too . . . obliging.” Effy couldn’t tell if he was trying to admonish her or warn her. Was it her he didn’t trust, or Ianto? It made her skin prickle. Surely he didn’t think she was so incompetent.
It's obvious that Preston just doesn't trust Ianto. He’s worried for Effy, not that he thinks she's incompetent. (But *I* do. 😐)
But Effy is so used to being underestimated and demeaned that she is quick to see the worst in his behavior.
