The two characters featured in the game are actually played simultaneously. However, your partner will not actually be controlled via artificial intelligence. Essentially, to move your partner from place to place, you'll simply hold down the L1 button to get him or her to follow you. Confused? It may sound strange, but it didn't seem all that complex. Along the same lines, you can switch to either Jake or Emily on the fly. The game will feature a number of puzzles that will require switching between characters. As each character is designed somewhat differently--Jake being more aggressive and handy with weapons and Emily being meeker and capable of projecting psychic powers--each character will be handier at tackling different tasks. You'll also occasionally need to work in tandem to complete objectives. In one example, we saw Emily crawl through a tunnel that only she could fit through to run around a corner and unlock a gate. Obviously, there will be more-complex puzzles than this, but this is a simple example of the kinds of things you might see.