Indaryn had an affair with Haelga, thus involving him in the quest Caught Red-Handed. Indaryn's Mark of Dibella must be obtained from him. Find him at the Black-Briar Meadery in the daytime (he is usually on the lower level), ask him about the Mark, then persuade him to hand the Mark over. This is the easiest Mark of the three to obtain. It's also possible to pickpocket him in order to obtain the mark as well. If the Dragonborn kills Indaryn before completing the Mark of Dibella quest for Svana Far-Shield, the quest will fail automatically.
Indaryn can be killed very easily at the Bee and Barb during the evening, when the inn is filled with people. If the Dragonborn drops an item or piece of equipment on the ground, Asgeir Snow-Shod and his father may attempt to grab it but will be interrupted by Indaryn. This results in a swordfight between the three, usually ending in Indaryn's death, because the Snow-Shods are essential for most of the game. The same may also happen with Mjoll and Aerin but is less likely. If Indaryn dies in either way before the Mark of Dibella quest is completed for Svana Far-Shield, this possibility will also fail the quest automatically.