Hints are broken down into three Tiers. Start with Tier 1 and only proceed to subsequent tiers if you are still truly stuck. By the time you get to Tier 3, the solution will be laid out clearly.
Tier 1: General Interrogation Tactics
Hint 1.1: Be Specific
Don't just ask "What did you do last night?" Ask "Where were you at 9:30 PM, when the carol singers arrived?" Precise questions get precise answers (or precise lies).
Hint 1.2: Use Information as a Weapon
If you learn something from one suspect, use it to challenge another. For example: "I spoke to Marcus, and he said…" This is the key to breaking their prepared stories.
Hint 1.3: Follow the Motive
Everyone seems to have a motive. Ask about them directly. "I hear you're in debt, Marcus."; "Lady Beatrice, was your marriage a happy one?"; "Eleanor, how badly did you need that money?"
Tier 2: Specific Lines of Inquiry
Hint 2.1: The Unhappy Marriage
Lady Beatrice is hiding more than just unhappiness. She had a major argument with Alistair just before he died. Confront her about the "divorce" or her "affair."
Hint 2.2: The Blackmail Plot
Marcus's story about "reconciliation" is a lie. He was trying to blackmail his father. Ask him what "Thomas Vance" has to do with the family fortune.
Hint 2.3: The Silent Witness
Mr. Hobbs sees everything. He knows who was moving about the house during the key moments. Ask him exactly who he saw near the study when the carol singers arrived.
Tier 3: The Solution
Hint 3.1: The Opportunity
Mr. Hobbs will reveal that Dr. Vance entered the study alone while everyone was distracted by the carolers. This is the 90-second window the killer needed.
Hint 3.2: The Motive
Once you learn the name "Thomas Vance" from Marcus, you have the motive. The final step is to connect that name to the person who had the opportunity.
Hint 3.3: The Final Accusation
The killer is Dr. Isabelle Vance. Her grandfather was Thomas Vance. She poisoned the port as revenge for her family's ruin. Confront her with all three facts: her name, her opportunity (seen by Hobbs), and her motive (revenge).