How to serializing object in an unreferenced assembly?

[NetWalker]

I am trying to serialize object using BinaryFormatter like below:

//========================
void SomeFunction()
{
SomeClass anObject;

BinaryFormatter bf = new BinaryFormatter();
MemoryStream ms = new MemoryStream();
bf.Serialize(ms, anObject);
.....
ms.Seek(0, SeekOrigin.Begin);
SomeClass aCopyObject = (SomeClass) bf.Deserialize(ms); // <==
exception?
}
// ========================

It works like a charm if I put these code in any assembly referenced.
However, when I place all these things (including the class "SomeClass")
into a dynamically loaded assembly (with name "plugins"), I got an exception
on deserialization. The error message tell me it "Cannot find assembly
'plugins'", while the error is raised by the code INSIDE the assembly
"plugins". When I add the plugins.dll back to the reference, it works again.
So I assume it searchs for assemblies within its reference list only.

Is there any work around I could use without writing my own deserializer?