Help with Virtual Methods Objective.

I am not sure what I am doing wrong. The error I received was:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.IndexOutOfRangeException: Index was outside the bounds of the array. at Treehouse.CodeChallenges.RepeatDetector.Scan (System.Int32[] sequence) <0x405205d0 + 0x00049> in :0 at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&) at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00038] in /builddir/build/BUILD/mono-4.4.2/mcs/class/corlib/System.Reflection/MonoMethod.cs:295 --- End of inner exception stack trace --- at Treehouse.CodeChallenges.Helpers.ReflectionHelpers.Call[T] (System.Reflection.MethodInfo method, System.Object instance, System.Object[] args) <0x4051fde0 + 0x00027> in :0 at MonoTester.Run () [0x00118] in MonoTester.cs:95 at MonoTester.Main (System.String[] args) [0x00013] in MonoTester.cs:29

namespace Treehouse.CodeChallenges
{
    class SequenceDetector
    {
        public virtual bool Scan(int[] sequence)
        {
            return true;
        }
    }
}

namespace Treehouse.CodeChallenges
{
    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {
            bool WellIsIt = false;
            for(int number = 1; number<=sequence.Length ; number++)
            {
               if(sequence[number - 1] == sequence[number])
               {
                    WellIsIt = true; 
               }
               else
               {
                    continue;
               }
            }
            return WellIsIt;
        }
    }
}