When Mr Jack Ngui was leaving for work on 28 July, he found a black bicycle that did not belong to him outside his flat. Attached to the bicycle was a white envelope.

But as he was running late, the 33-year-old manager did not think much about it.

When he returned home that evening, the bicycle and the envelope were still outside his 14th-storey flat in Block 625, Jurong West Street 61.

Then he saw that his unit number was on the envelope and realised that someone had deliberately left the bicycle for him.

Inside the envelope was a one-page handwritten letter of apology from someone who had signed off as 'Depressed Teenager'.

The letter writer confessed to stealing the bicycle from Mr Ngui's unit about four years ago, and was returning it because he felt remorseful.

But Mr Ngui, who lives with his wife and his sister in his three-room flat, told The New Paper that the bicycle did not belong to him.

He said he does not own a bicycle, and had moved into the flat only in November 2005.

SORRY

In the letter, the writer said: 'I am terribly sorry for whatever I did... I want to correct my mistake.'

The writer also said that he was an adopted child and that his 'uncle' and 'aunty' had not treated him well.

'I wanted to go jail because staying with them was worse than jail and so the only way to go to jail is to commit a crime.'

He said he regretted his actions later and decided to return the bicycle after living with the guilt for a few years.

But if Mr Ngui is not the owner of the bicycle, who is?

'At first, I thought it could have belonged to the previous owner of my flat,' said Mr Ngui.

But when he checked with his neighbours, a married couple, he discovered that the bike may have belonged to them.

His neighbour, Mr Krish Ng, 32, said his family's bicycle had gone missing about four years ago.

Mr Ng, 32, and his wife have been living in the flat for the past five years.

Although the bicycle they lost was red, a closer inspection of the returned bicycle showed traces of red paint beneath the black.

PAINTED OVER

Mr Ng said: 'Perhaps it was painted over. The bicycle is most likely mine.

'There were some other changes besides the colour but I can't remember everything about the original bike.'

The thief had admitted to modifying the bicycle in his letter but did not specify what he changed.

The Ngs said it had been so long since their bicycle went missing that they had forgotten about it.

In his letter, the thief asked to be forgiven.

He wrote: 'If you guys really, sincerely want to forgive me... I hope that you hang the national flag for at least 5 days upon receipt of my letter.'

But the Ngs said they do not have the Singapore flag and are not planning to buy one.

Mr Ng said: 'Asking us to hang up the flag is not the right way.

'If he sincerely wants to be forgiven, he can knock on my door and talk to me and then I will forgive him.'