This is on the basis that they murder Leanne, and it's announced (probably breakfast) who knew about the shield:How?
1) meet Charlotte and warm her
2) if she doesn't save Freddie, he could go out at the next round table. He's allowed to say he was a faithful all game, and just recruited. Prior to that, he'll know he's going, so he just needs to say 'I'm convinced Charlotte is traitor' and not talk about anyone else. Just repeating, 'If she's in at the end, she'll take all the money. Call it a hunch.' Then when he reveals he's just been recruited, they'll know she's a traitor.