"Oh, I'm not blaming anyone but myself. If I'd stayed back there the volcano would have popped out here somewhere, or else waited until we were gone." "If it is a volcano. Dr. Burkett didn't seem quite sure." "No, and I'll bet a nickel she's suiting up right now to go out and see. I hope she comes back with something while we're still near enough to hear about it." Hargedon shrugged. "I suppose it was also just your luck that sent you on a Darkside trip? You know the radio stuff. You knew we couldn't reach as far this way with the radios. Didn't you think of that in advance?" "I didn't think of it, any more than you would have. It was bad luck, but I'm not grousing about it. Let's get on with this job." Hargedon nodded with approval, and possibly with some surprise, and the tractor hummed on its way. The darkness deepened around the patches of lava shown by the driving lights; the sky darkened toward a midnight hue, with stars showing ever brighter through it; and radio reception from the _Albireo_ began to get spotty. Gas density at the ion layer was high enough so that recombination of molecules with their radiation-freed electrons was rapid. Only occasional streamers of ionized gas reached far over Darkside. As these thinned out, so did radio reception. Camille Burkett's next broadcast came through very poorly. There was enough in it, however, to seize the attention of the two men in the tractor. * * * * * She was saying: "--real all right, and dangerous. It's the ... thing I ever saw ... kinds of lava from what looks like ... same vent. There's high viscosity stuff building a spatter cone to end all spatter cones, and some very thin fluid from somewhere at the bottom. The flow has already blocked the valley used by the Brightside routes and is coming along it. A new return route will have to be found for the tractors that ... was spreading fast when I saw it. I can't tell how much will come. But unless it stops there's nothing at all to keep the flow away from the ship. It isn't coming fast, but it's coming. I'd advise all tractors to turn back. Captain Rowson reminds me that only one takeoff is possible. If we leave this site, we're committed to leaving Mercury. Arnie and Ren, do you hear me?" Zaino responded at once. "We got most of it, Doctor. Do you really think the ship is in danger?" "I don't know. I can only say that _if_ this flow continues the ship will have to leave, because this area will sooner or later be covered. I can't guess how likely ... check further to get some sort of estimate. It's different from any Earthly lava source--maybe you heard--should try to get Eileen and Eric back, too. I can't raise them. I suppose they're well out from under the ion layer by now. Maybe you're close enough to them to catch them with diffracted waves. Try, anyway. Whether you can raise them or not you'd better start back yourself."