The Walking Dead: A New Frontier's (i.e. Season 3) fourth episode, Thicker Than Water, is due on 25th April for PS4, Xbox One, PC, iOS and Android platforms.
That's a pretty quick turnaround, given that the last episode came out only a month ago. Prior to that there was a three month gap between the two-part season premiere and the third episode.
Thicker Than Water will continue the misadventures of the Garcia family and series stalwart Clementine, as the southern refugees continue to make their way through the post-apocalyptic remnants of society. Also, there are zombies.