The last we saw of Mace Tyrell he was being sent by Cersei to deal with the Iron Bank of Braavos, and he finally arrives there this week, according to the synopsis. That means another appearance by Mark Gatiss Tycho Nestoris, who was last seen agreeing to fund the war effort of Stannis. As he says though, the only thing the Iron Bank care about is numbers, so his loyalty will be to whoever can pay. With the crown very much struggling in its debts to the Bank, quite how bumbling Mace Tyrell deals with this is something likely to have ramifications back in Kings Landing.