score:1

Accepted answer
var combined = from c in careplans  
where c.patientid = 'e4a1da8b-f74d-4417-8ac7-b466e3b3ffd0'   
from lr in latestreferral.where(r => r.careplanid == c.careplanid).defaultifempty()   
from p in patients.where(patient => patient.patientid == ((lr != null) ? lr.latestreferral.patientid : -1)).defaultifempty()   
select new { c.careplanid, patientname = (p == null) ? "no patient" : p.patientname, latestreferral = (lr == null) ? null : lr.latestreferral };

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