BEIJING - The apartment appears exactly as they left it. Her purses hang near the door over racks of his shoes. The curios and wine glasses are arranged in matching cabinets and toys are stacked neatly on shelves. On a whiteboard in the hallway she has written the schedule of music classes for the boys.

It was only a short vacation they were taking to a beach resort in Vietnam. Muktesh Mukherjee thought his wife, Bai Xiaomo, deserved a break from the pace of raising their two sons. Her mother would look after 7-year old Mirav and 2-year old Miles as she often did. The Canadian couple could take the red-eye from Kuala Lumpur that would get them back to Beijing as the kids were waking that Saturday and they could all have the weekend together.

When they left they told the boys they would be back in a week. Then they closed the door on the purses and toys and souvenirs from past trips and vanished.

“I don’t think they are dead,” said Zhang Mei Ling, Ms. Bai’s mother. “I still believe that my daughter and son-in-law are somewhere and waiting for people to rescue them. I just don’t know where exactly they are.”

Mrs. Zhang passes the days caring for her grandsons and watching the news, hoping some of it will be good enough to end the nightmare of not knowing. She does not believe Malaysian officials who declared flight 370 lost. For her it does not add up: A plane changes course, flies for hours and proves invisible to even the most-advanced technology in the world. Was it hijacked? Maybe. Was there secret cargo? Perhaps. Did it land somewhere? It must have. Until there is evidence or an explanation, she says, her daughter is alive.

We first met Mrs. Zhang the night the families of MH370 passengers were told by text message – in English, not Chinese – that Malaysian officials declared that the flight had ended in the southern Indian Ocean. They gathered at the hotel where many had held vigil for weeks. Mrs. Zhang burst out of the meeting room, distraught and furious at “their lies”, and yelled for China’s government to intervene. That her own mother passed away the day after Ms. Bai and Mr. Mukherjee went missing has left her and her family disfigured by grief.

“Can you imagine the blow?” she asked that night in the hotel's basement hallway. Then she crumpled and cried and whispered that they cannot bury her mother until her dearest daughter is home.

We talked again the next evening in the choreographed calm of Ms. Bai’s living room that bore all of the fixtures and features of a young family. A piano in one corner, a child's drum set in another. Bookshelves were lined with educational DVDs and boxes of Lego. Most of the frames hanging on the walls were family portraits of the boys with their doting parents.

And then there was Miles.

He greeted us at the door in a superhero t-shirt, smiled hello and declared, “Mommy is on a trip!” His grandmother’s eyes welled with tears and she turned away because she has tried not to cry in front of him.

“He doesn’t understand,” she said, “He always asks, where’s mommy? How do I answer him?”

With 26 countries involved in the search that answer has proved among the most elusive in aviation history. The assumption for now is that flight 370 went down in a remote stretch of treacherous sea. Why it lost communication and flew thousands of kilometres off-course to end there will remain a mystery until the plane’s black box is recovered. That may prove impossible in one of the most hostile environments in the world. The waves swell and the wind gusts and together they form currents strong enough to carry debris into a completely different part of the planet. Ships, aircraft and a high tech black box locator are scouring the search zone.

None of the resources or experts has yet answered Miles’ question that he asked several times during our visit. We surveyed his collection of trains and marveled at his Frisbees. He played a music video on his iPad over and over so we played air guitar and danced. There was peekaboo from behind the piano, a quick set on the drums and then he sat on the couch and asked again, Where’s mommy?

Mirav, who will be 8 in May, was with Muktesh’s parents who traveled to Beijing when they got the news of the flight’s disappearance. Mrs. Zhang sighed that Mirav is struggling. He knows his parents are late coming home because their plane somehow lost its way. He told his grandmother he is saving his money so he can go find them.

“I don’t believe the Malaysian officials,” said Mrs. Zhang. “From the very beginning I do not believe it. Really.” She showed us the vacation photos the couple posted to their Facebook pages: By the pool. Going for dinner. Hugging.

The day before the flight she did a video call with her daughter.

“We had a great time,” said her only child, smiling. “See you tomorrow.”