I would like to ask somebody what is the meaning of the bold text.

"Grimshaw has murdered a man," he said briefly. "I want you to help me. Come to Cheyne Walk. Take a cab.
Of course I went, with a very clear vision of the future of Dagmar, Lady Cooper, to occupy my thoughts during
that lurching drive through the slippery streets. I knew that she was at Broadenham, holding up her head in
Grimshaw's house was one of a row of red brick buildings not far from the river. Doctor Waram himself opened
the door to me.
"I say, this is an awful mess," he said, in a shocked voice. "The woman sent for me—Levenson, that actress.
There's some mystery. A man dead—his head knocked in. And Grimshaw sound asleep. It may be hysterical, but I
can't wake him. Have a look before I get the police."

Mildred Cram, Stranger Things, 1923

Thank you