You will regain control of Acarno in a hallway being chased by several guards. Ignore the shots and run forwards, as these enemies re-spawn infinitely. Keep running forwards, past the blue and pink hologram in front of you (turning left or right will result in game over), and into the black opening at the end of the hallway.
Emerging in the next room, take cover behind the three pillars on the right hand side – the guards will continue to shoot, but not follow you around the pillars which will allow you enough time to restore your health.
There are now some secret items to collect – start by equipping the SHEILD JACKET, SHOCK ABSORBER BOOTS and ensure the GRAVITY CONTROLLER is turned on.