A steadier ground guide to discovering that a stranger has been working on him, sometimes for weeks. What's usually behind it, what to say that won't drive it into hiding, and when to bring in outside help. If money left his accounts in the last few days, call his bank's fraud line before reading any further.
Notice the heat of it, the fury at whoever did this and the flash of "how could he" aimed at him. The second one will reach him first if you let it, and it's the one most likely to send the next phone call into hiding.
Before anything else, ask whether this is new for him. A man who has always been careful with money and now believes a caller claiming to be from the government, or sends savings to an online friend he has never met, may be showing you a change in judgment before his memory shows one. Researchers who followed older adults for several years found that people less able to recognize scams were about twice as likely to later develop mild cognitive impairment or Alzheimer's disease, so if there's no diagnosis yet, this belongs in front of his doctor. One hard distinction belongs here too. If the person taking money is someone he knows, a relative, a neighbor, a paid helper, this guide isn't the right tool, and that's a call for Adult Protective Services.
The scam works on him because of what it gives him as much as what it takes. The caller who phones every afternoon offers attention, the grandson in trouble lets him be the one who rescues, and the prize or the investment promises he can still provide. Dementia can wear down the ability to judge another person's intentions well before it takes the ability to hold a warm conversation, so a patient stranger can feel more trustworthy than a worried son asking pointed questions. Scammers count on this, and many tell their targets to keep the arrangement from family who won't understand. When he defends the caller, hides the mail, or gets angry that you asked, he may be protecting something that feels real to him, and doing exactly what he was told to do.
What decides your next move is whether money is still moving. If it already happened and the contact has stopped, the work is recovery and repair: report it quickly, and make it safe for him to tell you next time, because shame keeps many older people silent after they've been fooled. If the calls, letters, or messages are still coming, the conversation about what happened can wait. Stopping the flow comes first, through his bank, his phone, and his computer, and it usually has to happen alongside him rather than by persuading him, since someone who believes the story can't be argued out of it in one sitting. Unless someone holds legal authority over his finances, the money and the decisions are still his, which is why the fastest route runs through him and his bank rather than around him.
When talking him out of it isn't working, stop trying to win the argument and change what the scammer can reach.
For the next week, write down every call, letter, or message he mentions or you see that asks for money or personal information, with the date, the name used, and the amount requested. This is exactly what the bank, the police, and a fraud case manager will ask for, and it shows whether the contact is fading or finding new ways in.
Print the one-page log if you want somewhere to keep this, and take it to the appointment.
This is what the tracking is for. Dates, names, and amounts turn "I think he's being scammed" into something a bank, a police officer, or a case manager can act on.
The scammer found the parts of him that still trust and still want to be generous. Your job is to put a fence around those parts so he gets to keep them.