By Mark Stone, Asia Correspondent
Exactly a year ago, Wang Le was preparing for his mother's return from a holiday in Malaysia.
Zhang Chi had been to Kuala Lumpur with a friend. She sent her son a text message just before leaving. "At Kuala Lumpur airport" it read. She then boarded her plane for Beijing: Malaysia Airlines flight MH370.
"I miss my mum every day," Wang Le says.
"Many moments I think 'Hmm, maybe I should call her now'. I want to call her, but I cannot. Too many memories."
We have joined him for dinner at his father's Beijing apartment. Wang Le and Wang Yongzhi spend every weekend together.
The two men, father and son, look after each other. Really though, it is clear that Wang Le is his father's support. Wang Yongzhi appears to be a broken man.
"Some times he misses my mum too much and he puts a bowl here and chopsticks here and he feels like he's having dinner together with my mum," Wang Le says.
They show me to a bedroom. "This is my mum's room," Wang Le says.
"Everything is not changed. The same as when she lived. Everything the same," he says.
The room is precisely as it was a year ago. Zhang Chi's makeup sits on a dressing table. The bed is made. Some washing hangs in the window.
The only change is a collection of white origami birds. Wang Yongzhi makes one almost every day in memory of his wife.
"Today is your birthday" he has written on one. "It is February already" another says.
As if to cruelly compound their grief and remind them of their loss, the apartment is under the Beijing flight path. Overhead every few minutes is the noise of a jet.
They know it makes no sense to leave the room untouched, but then none of this tragedy makes sense. Over and over again, they have asked themselves how a plane can simply disappear.
MH370 disappeared from radar shortly after taking off from Kuala Lumpur airport in the early hours of 8 March, 2014, bound for Beijing.
A total of 239 people including crew were on board the flight. Searches first took place in the South China seas before radar data concluded it had veered west off course and over the Malay peninsula. The searches then shifted to the Andaman Sea.
However, painstaking analysis of satellite data from British company Inmarsat eventually concluded that the plane had flown south for up to eight hours before coming down in the southern Indian Ocean off the western Australian city of Perth.
An initial surface search of that area involved 22 military aircraft and 19 ships from eight countries. They covered search areas of more than 4.6 million square kilometres.
Since then the focus has been an extremely challenging search of the seabed within a 'priority search area' which was determined by further satellite analysis.
Currently, four ships from the Dutch firm Fugro are scanning a mountainous 60,000 square kilometre seabed.
The search is being jointly funded by the Malaysian and Australian governments and coordinated by the Australian Transport Safety Bureau (ATSB).
A little over 40% of the area has been searched with no sign of the plane. The search is due to be complete by May.
"Of course she knows we miss her. She is my mum and we have a very, very good relationship just like friends and we can talk [about] everything. We like to 'date' every week," Wang Le tells us.
I ask if he and his father blame anyone for what has happened. "We don't know what happened exactly, we don't know the truth so [to] blame anyone is not helpful," he says.
"For me I just think if my mother can see me, she can watch me somewhere. She doesn't want to see her son very sad every day so maybe she is happy to see me work hard and take care of my father, my grandmother, my whole family."
