Sir, You Are Being Hunted's promised multiplayer mode has finally come to fruition. It broadly follows the premise of the single-player game—human trapped on a procedurally generated island, tasked with finding bits of a portal thing while evading tweed-clad deathbots—but obviously makes a few changes to accommodate those extra players. Firstly, and most importantly, only one player can actually escape the island and win, so be prepared to betray your friends if you want to survive.
Secondly, those fragments you need to collect will only be active at specific times. Thirdly, you can only visit a single island. And fourthly, obviously, there are also some extra humans knocking about—humans you can trade with, should you desire.
Sir should have been updated now, regardless of where you bought it, and you can find details of how to set up and play a multiplayer game here. Ben Griffin wasn't too keen on the game when he reviewed it last year, but if you like procedurally generated British moors and robots in top hats, then it might be very much your thing.