He really didn't like employing it, but he was at his wits end practically, and it hid his frustration. Frustration at his inability to understand this and make it work when it was so crucial, that there was some other part of him, some alien thing inserted into his body, that he had no control over.

"Feel for the source of the energy," he repeated, making a clicking sound between teeth and tongue. "Easier said than done, I think."