Leftrin is the captain of the liveship barge Tarman. He immediately falls in love with Alise when she boards his ship in Trehaug on the way to Cassarick, and this love is one of the major reasons why he signs up on escorting the dragons and their keepers to Kelsingra.
Leftrin had Tarman improved by using wizardwood from a log he found. Because this is illegal, he gets blackmailed by a Chalcedean merchant, Sinad Arich, into smuggling dragon parts to Chalced, but in the end refuses to do this.
Because of the class difference and the fact that Alise is married, they both decide not to act on their feelings, but after Alise hears of Hest Finbok's romance with Sedric Meldar, she decides that their marriage contract is void, and starts sleeping with Leftrin, and by the time they reach Kelsingra, they are a couple.