So, the boy was here, was he? Well, so much the better - he could get rid of that nuisance once and for all. If it wasn't for him, the old man could never have bought his shop and got in his way.
By the time Ethan got to the first floor the smell of fuel was intense. A discarded petrol can lay in one of the deserted flats, its contents dripping down the walls and pooling on the floor.
Months before, Chan had hired thugs to start a small blaze in the ally behind the building, part of a campaign of intimidation designed to force the remaining residents out. A chill ran through Ethan as he realised that this time, however, Chan planned to torch the whole building.
"I'm calling the police!" Grandad yelled from the ground floor, as, from an upper storey, the sound of footsteps echoed down the narrow staircase.
Knowing it could be too late by the time help arrived, Ethan began to climb once more. He found each floor of the building primed to explode into flames. At the very top of the stairs, the door to the roof was swinging open.
As he stepped cautiously out into the night sky, a shove in the back pitched Ethan forward onto his knees. He turned to see Chan between him and his only escape route.
"You don't think you'll get away with this, do you?" Ethan demanded, now beginning to comprehend the seriousness of the situation he'd got himself into.
Grinning malevolently, Chan advanced on him. "You're the only one who's seen me and you're not going to be telling anyone."
Regaining his feet, Ethan vaulted the low wall that separated the two halves of the roof, and Chan followed.
"They'll say you leapt from the building to escape the fire," Chan explained as, with outstretched arms, he relentlessly shepherded Ethan away from safety. "It will be a terrible tragedy and everyone will be so traumatised." He laughed. "Well, almost everyone."
Soon Ethan found himself with his back to the parapet. He looked over the wall and across to the neighbouring building. The two buildings were separated by an alley that was narrow, but not narrow enough. He glanced down into the six-storey drop.
The events of the next few moments seemed to happen almost simultaneously. As Ethan leapt up onto the parapet, Sam and Yiu-hon burst out of the doorway to the stairwell. And when Chan lunged forward, Ethan took a step back and plunged vertically downwards.
Ethan had no idea how long he could hang on for, or for how long the metal struts that attached the air conditioning unit to the outside wall would hold. Thankfully, he was pulled in through a window by a police officer before he could find out.
Chan tried to claim he was attempting to save Ethan, but with the cameras on their phones, Sam and Yiu-hon had documented what really happened.
"I knew Chan was a crook the moment I met him," Ethan's mother fumed, when her son eventually returned home late that evening. "But what I still don't understand is what his arrest has got to do with you."
Ethan exchanged a furtive glance with his grandad. If the police came around to interview him at home, she would surely discover the truth.
So, with some trepidation, he made her sit down.
"When I stopped Chan from burning down gung gung's building, he tried to throw me off the roof," Ethan confessed.
His mother looked at him for a moment before, to his and Grandad's amazement, roaring with laughter. "And I thought you weren't going to tell me any more lies," she said, slapping the arm of her chair.
There was undeniably a lot to be happy about. The future of Grandad's shop was secure and his neighbour Mr Wong, now recovering well from the injury he sustained in Chan's attack, could sit and watch as a willing Yiu-hon helped Grandad clean up his store.
However, as the week wore on, Maya's imminent departure for Britain cast a deeper and deeper shadow over Ethan's life. Despite what she said, he knew she wouldn't be back for visits every holiday. And he also knew that the sooner she got on with her new life, and he with his, the better.
That's why, though it was hard, he preferred to leave her text messages unread and her e-mails unopened. Ultimately, it was less painful to accept it was over than to accept her sympathy.
Nevertheless, Ethan's mood did not go unnoticed. And, knowing how stressful her illness, and the burden of supporting the family, had been for him, his mother found his current suffering unbearable.
The rain was hammering against her bedroom window, as Maya zipped up her case and took one final look around. Yet, however grim the weather, it couldn't come close to matching the bleakness of her mood as she prepared to leave.
At that very moment, Ethan's mother and grandfather were sitting down in the office of his form teacher at St Jude's.
"I assume you're here to discuss Ethan's sudden fame," Mr Hemmings began. "The news he's behind shamefacebook has caused quite a stir in the school."
Mum allowed herself a small smile of pride before shaking her head. "Actually, we wanted to talk to you about something else."
"What's wrong?" Ethan asked when he saw Mum and Grandad waiting by the school gates, drenched by the unremitting downpour.
As his mother hesitated, his grandfather started. "Sui-man, when you get to my age and you look back at your life, you realise what really matters, what is really important to you, is your family, your friends and the adventures you've had."
With Ethan staring at him in blank bemusement, Mum picked up the ball. "Ok, what gung gung's trying to say is ..."
The brief delays at every red light were eternities of agony for Ethan.
As soon as he'd heard Mum and gung gung's news, Ethan had switched on his phone and, for the first time in a week, checked his messages. Like all the others, the last was from Maya, a dispirited text, explaining that she understood why he didn't want to talk and wishing him goodbye and good luck.
Now, sitting in the back of the taxi, Ethan continued to compulsively call her number long after it was clear he'd be answered by nothing but a recorded message.
By the time the taxi hit the highway after an uninterrupted if rain-spattered ride, Ethan knew he was already too late.
And sure enough, as they rounded the coast of Lantau onto the airport approach, a plane took off, bang on time.
To be concluded next week