Master White sat on a chair beside the table and faced them. “This is the most important piece of machinery in the harnessing process, our spectral oscilloscope, or as we like to call it, the GODAR: our Ghost Observation Detection and Ranging device. This screen allows us to visualize the signals. In time you will come to learn the inner workings of these systems.”

Master White took the key from around her neck and went through a door at the back of the room. She returned with a small wooden box. Prue recognized it straight away.

Master White opened the lid and gently took the qwortzite out as though holding a fragile egg. It glowed with kaleidoscopic colours. She placed it inside the machine body.

A long time passed as the two women examined and adjusted equipment, with Master Woolstenbury wearing her magno-viewers. They attached something to the main machine that looked like a dish.

“This is a parabolic reflector. We use it to focus the signal into a feed point,” said Master White.

Master Woolstenbury was adjusting the dials, looking at the signals streaming across the spectro oscilloscope. Prue strained to see them more clearly. She couldn’t help but wonder: was one of those squiggly lines Francis, trying to come through?

“Signals, Prue. They’re everywhere, we just can’t hear or see them all.”

Prue shook her head doubtfully. “How can they be there if we can’t see or hear them?”

“Take rats, for instance.”

“Did you say rats, Francis?”

“Yes. They communicate with each other at a range outside of human hearing.”

“Really?” Prue said, dismounting her mechanimal horse beside the barn.

“I’ve heard it on the signal generator, when I was testing the homing transmitter. Silent signals are how the transmitter works. It sends a message through the air, and the receptor on the machine picks it up.”

“That’s brilliant!” Prue said, amazed.

“Come on. I’ll show you how it works.” Francis smiled.

“Agapantha, can you hold this for a moment for me, please?” asked Master White.

Prue looked to Agapantha, the spell of her thoughts suddenly broken.

After a sideways glance at Prue, Agapantha tucked her russet hair behind her ears and went to Master White. “Just hold that dial right there… That’s it, give it a slight turn. Stop when it feels right.”

The signals seemed to pulse a little faster. After a moment, they became less tangled.

“Thank you, Agapantha. You have a knack for this. You can sit down now.”

Minutes later, there was just one pure signal pattern on the screen. Master Woolstenbury glanced at Master White, her eyes gleaming.