I purchased a new character from the tavern in order to switch out a party member, and as a result I spent the 10 gold hiring fee without actually receiving the character. There was no warning that I couldn't hire a fourth party member. If I'm only supposed to have a maximum of 3 characters in my party, shouldn't I be prevented from hiring new ones, so I don't go wasting gold by mistake?
In the tavern (or any shop) You can click-drag the screen to the right. You should see the list of currently unused characters. You should be able to see the character you purchased, remove one of your current characters from your party and add the new one using the buttons at the bottom of the character sheet. Hope that helps!