"I hate to admit that my judgment is that rotten, Carnes, but the evidence certainly points that way. At that, I think I'll reserve final judgment until later. Now, in view of what you have learned, I have a job for you." "It's about time, Doctor. I have been rather useless with all the high-powered science that has been flying around here." "Well, you'll be in your element now. We know that Denberg is loose and their capture of Thelma is no coincidence. I was pretty sure that Saranoff and his gang were at the bottom of this; now I am certain. They must have introduced something onto the marshes last night which caused the trouble. They could not have come overland very well, for the place is too well patrolled. Had they come by air, they would have attracted attention, even had they used a Bird silencer on their motor, for they couldn't muffle their propeller, especially on a takeoff, and there are plenty of men here who would have recognized it. You might check up on that, but I am confident that they came by water. Launches and boats are continually passing up and down the Chesapeake and its tributaries and one more could easily have escaped notice. The Bush River is at the far end of the Michaelville range and it is navigable for craft of light draft at high tide. Find out whether any strange craft were seen in the vicinity of the proving ground last night. If you draw a blank, go to Perryville and Havre de Grace and see what you can find out there. I have a hunch that their base is more likely to be up the Susquehanna than down toward the coast. Above all, Carnes, don't approach the proving ground by water to-night and don't get near the mouth of the Bush River." "All right, Doctor. What are you going to do?" "I'm going down on the swamp and collect samples. Oh, don't look so worried. I know just what I am up against and I will have adequate protection. I'll be in no danger and you would just be in the way. Toddle along, old dear, and report to me by telephone as soon as you have learned anything." "As you say, Doctor. You'll hear from me the minute I do." * * * * * When Carnes had left, Dr. Bird climbed into the waiting car and was driven back to the hospital. Captain Murdock greeted him with a smiling face. "I don't know how you got on to that treatment, Dr. Bird," he said, "but it is doing the men good. The worst cases haven't been affected much, one way or the other, but the progress of the malady in the mild cases from the stables has been completely checked. I think they have a chance now." "They'll be all right if the destruction and coagulation of tissue hadn't progressed too far before you checked it, Captain. Treat them now for simple lung cauterization and they ought to get well." "I have some more of those crystals dissected out, Doctor." "Keep them in the dark until Mr. Davis comes after them. I want to take a few of them back to Washington for study."