Investigators believe the key to how Belgian teenager Theo Hayez vanished lies with what happened at 1.02am at a beach on June 1, 2019.
After midnight, Theo used his phone to swap messages with his stepsister Emma, watch clips from a French quiz show, and joke with a friend on Facebook about an upcoming U2 concert.
But just after 1am, his phone stopped receiving data.
An inquest into the 18-year-old backpacker's disappearance in Byron Bay heard police believe he clambered up the beachside cliffs, dropped his phone, then fell and was swept out to sea.
Belgian teen Theo Hayez (pictured) was near the end of a backpacking trip around Australia when he vanished in Byron Bay, NSW, two years ago
His family, who travelled to Byron Bay from Europe for his two-week inquest in the NSW Coroner's Court, don't accept their cautious boy would do something so dangerous in the dark.
They said the only way he would climb the cliffs is if someone was with him, reassuring him it was safe.
The inquest previously heard Kristin Edwards, the counsel assisting the inquest found no evidence Theo was reckless, engaged in dangerous physical activity, or was particularly interested in drugs.
There was also no evidence, the inquest heard, to suggest the young traveller - who was to start an engineering degree when he returned home - would have taken his own life.
Whether Theo encountered anybody else that night is one of the major mysteries the inquest will explore.
Another is how he came to be on the Cosy Corner beach in the dark.
An inquest into the disappearance of missing backpacker Theo Hayez (pictured) in Byron Bay, the holiday hotspot where he was seen is expected to last two weeks
Theo Hayez's parents Laurent Hayez (left) and Vinciane Delforge (right) at Byron Bay Coroners Court on Monday as an inquest into his disappearance began
Theo's night began at his hostel, where he shared some goon (cask wine) with fellow backpackers before heading into town about 9pm.
At the Cheeky Monkey's bar, the group discussed European politics as they drank a few beers.
Never-seen before CCTV footage played at the inquest shows Theo dancing in the bar and chatting with friends hours before he disappeared.
He can be seen occasionally stumbling inside the venue before a security guard who thought he was swaying ejected him about 11pm.
However, the evidence he was actually intoxicated was 'ambiguous', Ms Edwards said on Monday.
The decision to kick him out on his own without any chance to tell his friends has caused Theo's family 'great distress', Ms Edwards told the inquest.
Theo then looked up directions to his hostel on Google Maps.
His subsequent decisions would be hard to believe if investigators didn't have Google data obtained by his family, Ms Edwards said.
Theo walked in the opposite direction to the route outlined on Google Maps. For seven minutes, he stopped at some cricket nets.
Next he took a dark track through bushland towards the ocean, at points appearing to walk quickly or run.
Police believe Theo may have slipped and fell into the ocean while climbing a cliff at night. Pictured: New South Wales police are seen in the Cape Byron State Conservation Area during a search for Theo on June 2019
The inquest heard Theo's phone stopped receiving data at 1.02am the morning he vanished. It mysteriously re-entered reception at 6.17am for a few hours. It has never been found.
At the urging of locals and police, coroner Teresa O'Sullivan walked the Milne Track one night last year.
Police noted it would be strange for a foreigner to walk the frightening and 'spooky' track alone at night - giving rise to theories Theo was with someone else.
He turned off the track into steep, dense bushland and ended up on the beach.
He was at Cosy Corner when he appears to have turned off his location services just after midnight to save battery.
His lighthearted messages sent in the next hour suggested he felt safe, Ms Edwards said.
Theo was last seen leaving Cheeky Monkey's bar (pictured) after he was kicked out by security guards
The Belgian teen (right) was captured on CCTV at a local liquor store hours before he disappeared
At 12.55am, he sent a message to his sister. Then 'something happened at 1.02am', Ms Edwards said.
'If we knew what that was, we think we probably would know what happened to Theo.'
That's when his phone stopped receiving data.
At 6.17am, it re-entered reception range and continued to receive data until lunchtime that day - indicating it did not fall into the water.
The phone has never been found.
Ms Edwards said the legal team had struggled to get data from Google, Facebook and Telstra to paint a fuller picture of that evening - in particular, whether anyone else was with Theo.
The inquest continues.
Lifeline
