Cass sent the patronus before she could even finish the sentence. He also made sure one was sent to Percy, and Susan. He needed help on a murder case and while Percy didn't like Susan, he trusted her more than most. More than anyone save for Percy. Besides they worked well together.
'He'll be here soon,' he said reassuring Dora, though as he meant to continue, urge her to get off the floor and go sit in a sofa or at a table, she spoke of Bellatrix and he looked around, then at her. There was something about the way she said looked that sounded...definite.
'Is that why you changed how you look?' he asked softly.