The email arrived at 6:41 on Tuesday, three days before the submission deadline, and Nadia read it twice before saying anything. Callum had written four hundred words about workload, family obligations, and a doctor's appointment he had postponed since August. Priya, who was soldering a connector, did not look up. "Just give us the gist," she said. Nadia set the phone face down on the bench. "He's out. He's taking the withdrawal option, and he's taking the flood-prediction module with him, because he wrote the whole thing on his own laptop." The soldering iron hissed against a damp sponge. Nobody spoke for a while.
Tomás arrived at seven with cold noodles and an explanation nobody wanted. He had known since Sunday; Callum had told him in confidence, and he had decided the news would keep until after the midterm. Priya put down her iron with theatrical care. "So you're culpable too," she said. "Not equally. But measurably." Tomás argued that Callum's code had always been the weak link, that the architecture was fragile, that the panel would have noticed anyway. Nadia interrupted before the argument could calcify into something permanent. Seventy-two hours remained. Blame, she pointed out, compiled no code and soldered no joints.
Nadia stepped into the corridor and called him. Callum answered on the fifth ring, his voice flattened by whatever he had taken to help him sleep. She did not ask how he was. She told him that the module belonged to the group, that the university's collaboration policy said so in plain language, and that she would raise the matter formally with Dr. Okonjo unless the repository was shared by ten o'clock. It was an ultimatum, and she disliked issuing it; Callum had once driven her to hospital at two in the morning. He said he would think about it. Then he hung up.
By nine they had a whiteboard and a problem that was no longer merely technical. The lab closed at eleven on weeknights; the makerspace required a supervisor; the only spare pressure sensors sat in a locked cabinet in the Civil Engineering annexe, and the technician who held the key was on leave until Thursday. Priya, who managed her sister's catering business at weekends, treated the logistics as a familiar species of puzzle. She drew a timeline, assigned each obstacle a name and an owner, and booked the six o'clock slot that nobody else wanted. Tomás volunteered to beg the technician by email.
At 6:12 on Wednesday, Nadia opened what remained of the project and understood the true scale of the damage. Callum's repository had come through at midnight, unannounced, with no message attached. The prediction model inside it was rudimentary — a single linear regression, trained on two months of rainfall data, commented in fragments. He had been bluffing in meetings since October. All those confident progress reports had described software that did not exist. Priya laughed once, without humour, and rested her forehead against the cold bench. "We've spent a term defending a ghost," she said. Nadia was already sketching what could be built instead.
The thing that galvanised them arrived at 9:40, in the form of Dr. Okonjo's weekly mailing list. The Thursday panel, she wrote, would now include a drainage engineer from the city water authority, who was scouting student projects for a paid summer pilot. Three groups would present. One would be funded. Tomás read the message aloud twice, and the second reading altered the temperature of the room. Priya abandoned her half-eaten breakfast. Nadia deleted her carefully worded apology to the panel, still unsent, and began writing a work plan instead. Ambition, it turned out, was more efficient fuel than grievance.
The sensors never came. The technician replied at noon from a campsite in Galicia, apologetic and unreachable, and the cabinet stayed shut. So they improvised. Priya gutted a discarded weather station from the recycling bins behind the physics building and harvested its barometric chip. Tomás assembled a water column from a two-litre bottle, a length of aquarium tubing and a bicycle pump, calibrating the whole contraption against a kitchen scale borrowed from the catering van. It looked absurd on the bench. It also produced readings accurate to within four percent, which exceeded the specification Callum had promised and never delivered.
What consumed them next was the housing. Tomás had an inordinate attachment to appearances, and he spent five hours of Wednesday evening laser-cutting an acrylic enclosure with chamfered edges and an engraved logo, while the software crashed repeatedly on Nadia's screen. She tolerated it for three of those hours. Then she stopped the cutter mid-job and handed him the debugging log instead. He protested that the engineer from the water authority would judge the object long before she judged the code. Possibly true, Nadia said. Entirely irrelevant at eleven at night, with a demo that could not run twice in succession.
At five on Thursday morning the model collapsed under live data, confidently predicting a flood in a fourth-floor corridor. There was no time to rebuild the architecture. What they could salvage was narrower and more honest: the sensor rig, which worked; the calibration method, which was genuinely novel; and a frank slide about the model's limitations. Nadia rewrote the presentation around the hardware and demoted the prediction to future work. Priya thought it sounded like a retreat. Tomás, unexpectedly, disagreed. Engineers, he said, respect a team that knows precisely which part of its own claim remains unproven.
The drainage engineer asked eleven questions, ten of them about the bottle-and-tubing rig, and offered them the pilot before lunch, on condition that the prediction work begin again from scratch under supervision. Dr. Okonjo noticed the missing fourth name and said nothing in public. Walking back across the quad, Priya proposed a rule: henceforth, no member of the group would report progress on anything that could not be demonstrated running, that same day, on a shared machine. Nadia agreed immediately. Tomás agreed more slowly, since the rule condemned his beautiful enclosure as well. Callum's laptop, wherever it was, stayed closed.