Having a coding issue that I can't figure out.... New to this and feel like I am missing something.

Creating a trigger on a joiner object (Horizon_Account_Cases__c) between cases and a custom object (Horizon_Account__c) which has only two fields (Horizon_Acct__c and Case__c) which are unique keys for the ID's on the two related object cases.  Upon triggering on Horizon_Account_Cases__c, the related case (eg Case__C) should have its field Related_Horizon_Account__c updated with the value in the joiner object that triggered (Horizon_Acct__c).  Can't get it to compile and need help!  I am sure I am missing something very obvious...

public class horizonCaseLinkUtil {
    
    public static void addHorizonToCase (List<sObject> linkIds) {
        try {
        
        List<Case> casesToUpdate = [select Id 
                                            from Case caseUsed
                                            where Id in :linkIds.Case__c 
                                                         limit 1];                                                         

        List<Horizon_Account__c> horizonAccounts = [select     Id
                                            from Horizon_Account__c hzActCase
                                            where Id in :linkIds.Horizon_Acct__c
                                                         limit 1];                                                         
                                                         
        for (Case cases : casesToUpdate) 
        {
            for (Horizon_Account__c horizon : horizonAccounts)
            {
                cases.Related_Horizon_Account__c = horizon.Id;
            }
            
        }
        update casesToUpdate;
        }
        catch (Exception e) {
            System.debut('Issue with the Horizon Case Update: ' +e.getMessage() );
        }
    }
    
}


trigger HorizonAcctCaseLinked on Horizon_Account_Cases__c (after insert, after update) {
            List<sObject> linkedHorizonCase = new List<sObject>();
            for (Horizon_Account_Cases__c hzActCase : Trigger.new)
                linkedHorizonCase.add(hzActCase);
            if (linkedHorizonCase.isEmpty() == false)
            {
                horizonCaseLinkUtil.addHorizonToCase(linkedHorizonCase);
            }   
}


@isTest(SeeAllData=true)
public class HorizonCaseLinkTest {
        static testMethod void caseLinkTestMethod() {
        List<sObject> sourceList = [SELECT Id 
        FROM Horizon_Account_Cases__c LIMIT 1];
        Case c = new Case(Subject = 'Test Case');
        Horizon_Account__c horizonAcct = new Horizon_Account__c (Name='Test Horizon Acct');
        if(sourceList.size() == 0) {
            sourceList.add(
                    new Horizon_Account_Cases__c(Case__c =c.Id, Horizon_Acct__c=horizonAcct.Name)
            );
        }
        horizonCaseLinkUtil.addHorizonToCase( sourceList );
        }
}