When the crew turned into their bunks on the Mercer Street oil tanker the buzz of drones spotted overhead earlier in the day was a fading memory.
A few hours later, the still night air of the Arabian Sea was pierced by a collision on the bridge and an immediate explosion that tore through to the living quarters, killing the ship's Romanian captain and a British security guard.
The tanker had been targeted by what US officials described as a fleet of “suicide drones” - unmanned aircraft loaded with explosives that self-detonate upon reaching their target.
Its victims died 175 nautical miles from the coast, tragic collateral damage in a growing proxy war between Israel and Iran fought in the shadows.
The trouble began some 80 nautical miles southeast of the Omani coast, where its crew first spotted a mysterious drone flying overhead.
An alert was sent to the Royal Navy’s UK Maritime Trade Operations (UKMTO) monitor, which urged other vessels to avoid the area.
The Mercer Street continued on its journey to the United Arab Emirates, passing by the Omani island of Masirah.
At around 3.40am local time on Friday, all hell broke loose in the Arabian Sea.
It is unclear how many aircraft were launched at the ship; but a fatal blow was struck by a drone that blasted a hole in the Mercer Street’s bridge and crashed into the living quarters.
A Romanian sailor, who was the captain of the ship according to Israeli officials, died in the blast along with a British security guard employed by the UK-based firm Ambrey Ltd.
At this point the UKMTO had issued a second alert which warned of a “vessel being attacked” 175 nautical miles northeast of Oman’s Duqm port.
In London, workers for Zodiac Maritime were scrambling for more details on what had befallen their vessel, amid confusing reports that suggested pirates were to blame.
It would take several hours before the ship would finally be met by US naval forces and escorted to a safe location - minus, sadly, the lives of two of its passengers.
"US Navy explosives experts are aboard to ensure there is no additional danger to the crew, and are prepared to support an investigation into the attack," said a spokesman for the US Central Command, which oversees American military operations in the Middle East, on Saturday. "Initial indications clearly point to a UAV-style (drone) attack," they added.
No state or militant group has claimed responsibility for the attack, but Western governments are already blaming Iran, which has a track record for striking Israel-linked vessels in the Gulf region.
Dryad Global, a maritime analyst group, said the attack had all the hallmarks of the so-called ‘shadow war,’ an escalating sea conflict in the Gulf where arch-enemies Israel and Iran have been accused of attacking each other’s ships.
The Mercer Street, a 600ft-long tanker, is owned by a Japanese company - but its operating firm in London belongs to Eyal Ofer, an Israeli billionaire and former Israeli Air Force officer.
It is not the first time that a ship associated with Mr Ofer’s Zodiac Maritime group has been caught up in an Iranian attack.
Earlier this month, the cargo ship CSAV Tyndall was set ablaze after an apparent drone attack which Israel blamed on Iran.
It is speculated that Iran had mistaken the vessel as being Israeli-owned, unaware that Mr Ofer’s company had sold the ship a few months earlier.
The shadow war is being fuelled by stalled talks in Vienna on restoring the Obama-era nuclear deal, as well as a series of suspected Israeli strikes on nuclear facilities in Iran.
Both sides are also accused of launching cyber attacks on key infrastructure targets such as ports.
Israel has repeatedly warned that Iran is on the brink of developing a nuclear weapon, and appears to have taken matters into its own hands by attempting to destroy the programme in Tehran.
Iran has not yet addressed claims it was behind the attack, though a report from the Iranian news network al-Alam claimed it was in response to an Israeli airstrike in Syria last week.
Al-Alam said that two “resistance fighters” had been killed during three Israeli strikes on Iranian targets in central and northern Syria.
Iranian attacks on Israel's assets are typically celebrated by pro-regime media. But the lack of coverage of the Mercer Street attack, excluding al-Alam’s report, suggests Iran's leaders did not intend to kill Westerners and are eager to distance themselves from the incident.
Speaking to the Sunday Telegraph, an Israeli official also suggested that the drone strike had been botched and vowed that the Jewish state would continue its "campaign" against Iran.
"Iran is spreading violence in every corner of the region," the official said. "Due to its enthusiasm for attacking an Israeli target, they have gotten themselves tangled up and have incriminated themselves by killing foreign civilians."
They added: "Iran's behaviour threatens the freedom of navigation and global commerce. Our campaign against them will continue."
Behnam Ben Taleblu, a senior fellow at the US Foundation for Defence of Democracies said Iran’s naval arsenal has become much more sophisticated in recent years.
“It would be no surprise to me that Iran would use a drone to carry out its tit-for-tat against Israel and maritime vessels. Iran has shown a gradual escalation in the maritime domain,” he said.
“This sort of tit-for-tat escalation is going to continue and Iran is likely to step up these attacks ... to signal that it will not take any cyber sabotage against it lying down,” he added.
The drones used in the attack are likely to have been either the Samad or Qasef models which have been used by Iranian forces as well as Iranian-backed Houthi rebels in Yemen.
They can carry an explosive payload of up to 30kg, a wingspan of at least three metres and can fly unaided for around 120 minutes at a time.
In January, Iranian media websites published pictures purporting to show new and unnamed drone models which looked similar to the Samad model.
Israeli analysts said that if it were confirmed that an Iranian suicide drone had been used then it would be a “major milestone” in the shadow conflict.
Seth Frantzman, the author of “Drone Wars,” said Iranian kamikaze drones usually used GPS to reach a fixed target and then explode, while in this case the drone had apparently followed a moving vessel.
This suggested, he said, that the drone may have been operated via remote control.
“This looks like a serious and complex attack that is not just a major escalation, but a new use of Iran drone technology,” he said.