A private investigator is offered a large sum of money by the opposing party to intentionally 'lose' crucial evidence. What is the investigator's ethical and legal obligation?

1. Accept the money and ensure the evidence is 'misplaced' without being traced back to them.
2. Report the offer to their client but proceed with the investigation as if nothing happened.
3. Immediately refuse the offer, terminate contact with the opposing party, and report the attempted bribery to their client and potentially law enforcement.
4. Consider the offer, as long as they can plausibly deny any wrongdoing later.