Dialog...

[Kerim]

This is a dialog in Tomb Raider AOD(Video Game). This is only a part of the dialog. I didn’t understand the following sentence.(Bold Texts).
…
C -You owe me an explanation. I'm waiting.
L -It's all a bit vague. I arrived at his apartment today from London. He was babbling with fear.
C -He said he'd tried to contact you.
L -He did. I never expected that. Not after Egypt.
C -Werner has been fearful for his life. He accepted a commission five weeks ago. Since then he's been acting strangely, jumping at shadows. He even left a package with me for safekeeping.
L -Package?
C -His notebook. Addressed to you.
…

[Ouisch]

Jumping at shadows - Someone who is extremely nervous or paranoid, so that any little thing frightens them. They'll get startled by the least little noise, or by something harmless like a shadow.