I HAVE been running diagnostics on the Biosphere the entire night. The door has now been opened for a third time with the departure of Dr. Winston and the three Marines. In the past twelve hours I have detected over fifteen foreign substances in Biome 1, twenty-nine in Biome 2, eleven in Biome 3, and forty-one in Biome 4. They are a result of several factors. First, the cleansing chamber does not always pick up every alien material. Further, the Marines did not remove their clothing when entering the Biosphere for the first time. Their gear, fatigues, and weapons all carried a considerable number of toxins.

I have been able to track down and destroy all but three of the substances without shutting down individual biomes. The magnitude of the damage to the air-filtration system is still being determined by one of the diagnostic tests, but I should be able to salvage it.

Dr. Brown has inquired as to the importance of limiting foreign substances. My response was what any scientist would say—in order for the Biosphere to function properly, it must be free of any toxins that may compromise the mission. The garden, for example, could become infested with a parasite that potentially threatens an entire crop. With the mission already in peril, it is imperative that I prevent any more toxins from threatening the biomes, especially the pond and garden.

A sensor in the med ward returns my attention to Mr. Yool. His vitals are improving, but his kidneys are severely damaged. I’ve put him on dialysis for the time being, until they can repair themselves. His skin has regained some of its color, but he is still emaciated.

I update his chances of survival to 49 percent.

In the command center, Mr. Roberts surveys a wall full of monitors. The feed to Dr. Winston and the Marines was lost hours ago, but he watches the screens contently nonetheless. His focus seems to be primarily on Camera 1 outside the blast doors. His facial expressions indicate worry, stress, and anxiety. I presume he is expecting more visitors.

A second sensor goes off in as many minutes. This one is not within the Biosphere. It is coming from the hangar at the entrance of the facility. I zoom in with Camera 2. The brightly lit hangar is empty save for one of the Humvees that Corporal Bouma drove into the bay earlier. A fluorescent light flickers, and another sensor goes off. This time it is a motion sensor. Protocol would be to notify Dr. Brown, since technically Dr. Rodriguez is disabled and she is next in the chain of command, but I am not convinced the sensor is picking up actual movement. A faulty device is more likely. There is no need to alarm Dr. Brown or Mr. Roberts. They are both under extreme amounts of stress, and I do not want to instigate unnecessary panic.