The Theft

Soon after the mission Adventures with Mali, you overhear an argument between Lee, Merlin, and Nora.

Lee and Merlin march off to talk to Gale. If you follow them, you'll witness more of the argument:

Go speak with Nora about the argument:

You ask her if the Locator Computer has been stolen, and she confirms that it's true.

Find Sam, who has been investigating, and speak with her:

She asks you to search around the Research Center to see if she missed any evidence. Search around the building until you find a hat. Show it to Sam and she will say that she thinks it belongs to Tuss. Meet Sam at Tuss and Huss's cave hidehout on the Bassanio Heights and explore the cave. At the end of the cave you will find the brothers talking:

Defeat them, retrieve the Locator Computer, and return it to Merlin. Realizing that she had wrongfully accused Nora and Lee, she will ask you to apologize to Nora for her. Mali will send you a letter soon after: