Bella's path veers off to the left, judging by the footsteps and occasional calls for "Sherlock?".

Sherlock's path - pitch dark with the loss of Bella's glowy thing, unless she chooses to set something on fire - divides, as best she can tell by listening to echoes and groping around, into stairs up and to the left, stairs down and to the right, and a scrunchy twisty passage that goes forward and slightly angled downwards.