This panel is a classic example of a golden age American comic book scene. It depicts a man, presumably Clark of the FBI, in a relaxed yet professional setting. He's seated in a wooden chair, leaning back with a casual posture that suggests he's been working for a while.

The man is wearing a gray suit with a white shirt, typical attire for an FBI agent in that era. On his head, he sports a fedora, adding to his detective-like appearance. In his right hand, he's holding a telephone receiver to his ear, indicating he's likely in the middle of an important conversation.

The setting appears to be an office, with a desk visible in front of the man. The background is predominantly dark, which creates a dramatic atmosphere and draws attention to the character and his actions.

A notable feature of the scene is a green lamp with a yellow shade positioned behind the man. This lamp is casting a bright light directly on him, creating a spotlight effect that emphasizes his importance in the story and adds to the comic's dynamic visual style.

The character's posture and the telephone in his hand suggest he's engaged in a conversation, possibly discussing a recent crime or assignment. This aligns with the text at the top of the panel, which mentions "Clark of the FBI keeps an all-night vigil."

Overall, the panel effectively captures the essence of a classic comic book detective story, with its stylized art, dramatic lighting, and character positioning all contributing to the narrative's atmosphere and tone.