Couple went on for a climbing trip. But only husband returned from the vacation and said that his wife slipped off...

Question

A couple went on for a climbing trip.
But only the husband returned from the vacation
and said that his wife slipped off while climbing and died.
On investigating, the local sheriff arrested him saying,
"Your travel agent called. You murdered your wife."

The man did not inform anyone about the trip.
Then how did the agent was so sure that it is a murder?

Answer 1

If the travel agent was so sure that the wife was murdered then it implies that he knows all about their travel plan.
Any anamoly in the couples travel plan like
1. A single ticket back to his place by the husband before hand
Or
2. Sudden change in the travel plans like cutting the trip short before hand
Could be clear implications which indicates that the husband expected his wife to die before she actually dies.