Expression and Demeanor: The guest might observe an unsettling expression on the murderer's face. He could appear furtive, tense, or even have a sinister grin, suggesting a hidden agenda. His body language could also reveal an air of secrecy, as he makes furtive movements or glances around the room.
Clothing and Appearance: The murderer might be wearing clothing or accessories that stand out or seem out of place in the formal gathering. Bloodstains or disheveled clothing could raise suspicion. Any unusual objects or weapons concealed about his person might also catch the attention of the guests.
Timing and Presence: The guests might find it strange if the murderer appears abruptly or seems out of sync with the rest of the guests. If they notice him lingering near the doorway, observing the room while staying on the periphery, this behavior might raise red flags.
Reaction to Macbeth: The guests might notice how the murderer reacts to Macbeth's arrival or how Macbeth responds to his beckoning. If there's a sense of urgency, discomfort, or agitation between the two individuals, it could arouse suspicion.
Disappearing Act: If the guests later notice the murderer's absence from the gathering or if he quickly slips away after beckoning Macbeth, this sudden disappearance might seem odd and warrant further investigation.
Eyewitness Accounts: The guests might later recall and discuss the murderer's behavior, leading to a piecing together of the events and uncovering his involvement in the crime.
It's important to remember that these are hypothetical observations and depend on the specific situation, the murderer's cunning, and the attentiveness of the other guests.