Xavier Mertz described the catastrophic event that took place on December 14, 1912:

At 4am, we were on the way back, but without our friend Ninnis. Our dear old Ninnis is dead.

This change is so rapid, that I can hardly believe it. In the morning Ninnis’ finger was better, and he had a good sleep (first time for the last three nights). He was happy and in a good mood.

Around 1pm, I crossed a crevasse, similar to the hundred previous ones we had passed during the last weeks. I cried out “crevasse!”, moved at right angle, and went forward. Around five minutes later, I looked behind. Mawson was following, looking at his sledge in front of him. I couldn't see Ninnis, so I stopped to have a better look. Mawson turned round to know the reason I was looking behind me. He immediately jumped out of his sledge, and rushed back. When he nodded his head, I followed him, driving back his sledge. At this precise moment, I thought that Ninnis must have fallen into a crevasse. Before, I just thought that he was a little way behind. The terrible truth was revealed during the next hours.

Inside a crevasse, at a depth of 150 feet, we caught sight of the back of Ninnis’ sledge. A faint dog’s moaning came up to the edge where we stood, straining our ears, calling and listening. We heard no other sound. I wanted to put the remaining sledge across the crevasse, and then climb down, but this was impossible, the crevasse was too wide, and our ropes too short. We absolutely wanted to do something, but what could we do?

Half an hour later, it was as silent as a grave in the crevasse. We were listening and listening, calling Ninnis, but to no avail. Our poor friend must be dead or unconscious. The crevasse, as wide as a sledge, with a depth of 150 feet, had a straight ice wall. Ninnis certainly died instantly. He would not survive, if he was only seriously injured and unconscious. In a glacier it is too cold at a depth of 150 feet.

We waited for hours, and then went more eastward, at a distance of about 5 miles. It meant the end of the sledging expedition. Later we came back. The dog’s moaning had stopped. We lowered a weight on a cord, which visibly hit a dog. He didn't move, obviously also dead.

The crevasse goes down deeper, and Ninnis must have crashed lower. We don’t know what really happened. Mawson heard nothing. He saw the sledge at a distance of 5 meters from the crevasse, and as usual cried: “crevasse, careful!” Ninnis was less than 10 meters behind Mawson. Everything must have happened in one second, because Mawson only heard a dog, humming a little. I heard nothing.

We could do nothing, really nothing. We were standing, helplessly, next to a friend’s grave, my best friend of the whole expedition. We read a prayer in Mawson’s prayer book. This was our only consolation, the last honouring we could do for our beloved friend Ninnis.

Our only comfort was the thought that the death was a straight path from a happy life. The ways of God are often difficult to explain.

At night, we were on our way home looking for accommodation and food. We only now realise that nearly everything, food, tent, ice-axes, shovels, had disappeared into the crevasse with the sledge. Mawson and I have to hold together, and with the few remaining things, to do our best to find the way back to the Winter Quarters.

— Xavier Mertz, Diary 14 December 1912. Translated from the original German by Robyn Mundy. © Robyn Mundy

Mawson later wrote in his diary what happened just after he had stopped to work out his position at noon:

A terrible catastrophe happened soon after taking latitude. My sledge crossed a crevasse obliquely & I called back to Ninnis … to watch it, then went on, not thinking to look back again as it had no specially dangerous features. After ¼ mile I noted Mertz halt ahead and look enquiringly back. I looked behind & saw no sign of Ninnis & his team. I … hurried back to find a great gaping hole in the ground. I called down but could get no answer …

We hung over the edge but could see nothing nor get any answer … we caught a glimpse of what appeared to be a food bag and one dog partially alive moaning … Our ropes not long enough to go down … Dog ceased to moan shortly. We called and sounded for three hours …

Read the burial service.

Reviewed our position: practically all the food had gone down … We considered it a possibility to get through to Winter Quarters by eating dogs, so 9 hours after the accident started back, but terribly handicapped …

May God Help us.